PSPP

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GNU PSPP Developers Guide

This manual is for GNU PSPP version 0.10.2, software for statistical analysis.

Copyright © 1997, 1998, 2004, 2005, 2007, 2010, 2014, 2015, 2016 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".


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1 Introduction

This manual is a guide to PSPP internals. Its intended audience is developers who wish to modify or extend PSPP’s capabilities. The use of PSPP is documented in a separate manual. See Introduction in PSPP Users Guide.

This manual is both a tutorial and a reference manual for PSPP developers. It is ultimately intended to cover everything that developers who wish to implement new PSPP statistical procedures and other commands should know. It is currently incomplete, partly because existing developers have not yet spent enough time on writing, and partly because the interfaces not yet documented are not yet mature enough to making documenting them worthwhile.

PSPP developers should have some familiarity with the basics of PSPP from a user’s perspective. This manual attempts to refer to the PSPP user manual’s descriptions of concepts that PSPP users should find familiar at the time of their first reference. However, it is probably a good idea to at least skim the PSPP manual before reading this one, if you are not already familiar with PSPP.


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2 Basic Concepts

This chapter introduces basic data structures and other concepts needed for developing in PSPP.


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2.1 Values

The unit of data in PSPP is a value.

Values are classified by type and width. The type of a value is either numeric or string (sometimes called alphanumeric). The width of a string value ranges from 1 to MAX_STRING bytes. The width of a numeric value is artificially defined to be 0; thus, the type of a value can be inferred from its width.

Some support is provided for working with value types and widths, in data/val-type.h:

Macro: int MAX_STRING

Maximum width of a string value, in bytes, currently 32,767.

Function: bool val_type_is_valid (enum val_type val_type)

Returns true if val_type is a valid value type, that is, either VAL_NUMERIC or VAL_STRING. Useful for assertions.

Function: enum val_type val_type_from_width (int width)

Returns VAL_NUMERIC if width is 0 and thus represents the width of a numeric value, otherwise VAL_STRING to indicate that width is the width of a string value.

The following subsections describe how values of each type are represented.


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2.1.1 Numeric Values

A value known to be numeric at compile time is represented as a double. PSPP provides three values of double for special purposes, defined in data/val-type.h:

Macro: double SYSMIS

The system-missing value, used to represent a datum whose true value is unknown, such as a survey question that was not answered by the respondent, or undefined, such as the result of division by zero. PSPP propagates the system-missing value through calculations and compensates for missing values in statistical analyses. See Missing Observations in PSPP Users Guide, for a PSPP user’s view of missing values.

PSPP currently defines SYSMIS as -DBL_MAX, that is, the greatest finite negative value of double. It is best not to depend on this definition, because PSPP may transition to using an IEEE NaN (not a number) instead at some point in the future.

Macro: double LOWEST
Macro: double HIGHEST

The greatest finite negative (except for SYSMIS) and positive values of double, respectively. These values do not ordinarily appear in user data files. Instead, they are used to implement endpoints of open-ended ranges that are occasionally permitted in PSPP syntax, e.g. 5 THRU HI as a range of missing values (see MISSING VALUES in PSPP Users Guide).


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2.1.2 String Values

A value known at compile time to have string type is represented as an array of char. String values do not necessarily represent readable text strings and may contain arbitrary 8-bit data, including null bytes, control codes, and bytes with the high bit set. Thus, string values are not null-terminated strings, but rather opaque arrays of bytes.

SYSMIS, LOWEST, and HIGHEST have no equivalents as string values. Usually, PSPP fills an unknown or undefined string values with spaces, but PSPP does not treat such a string as a special case when it processes it later.

MAX_STRING, the maximum length of a string value, is defined in data/val-type.h.


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2.1.3 Runtime Typed Values

When a value’s type is only known at runtime, it is often represented as a union value, defined in data/value.h. A union value does not identify the type or width of the data it contains. Code that works with union valuess must therefore have external knowledge of its content, often through the type and width of a struct variable (see Variables).

union value has one member that clients are permitted to access directly, a double named ‘f’ that stores the content of a numeric union value. It has other members that store the content of string union value, but client code should use accessor functions instead of referring to these directly.

PSPP provides some functions for working with union values. The most useful are described below. To use these functions, recall that a numeric value has a width of 0.

Function: void value_init (union value *value, int width)

Initializes value as a value of the given width. After initialization, the data in value are indeterminate; the caller is responsible for storing initial data in it.

Function: void value_destroy (union value *value, int width)

Frees auxiliary storage associated with value, which must have the given width.

Function: bool value_needs_init (int width)

For some widths, value_init and value_destroy do not actually do anything, because no additional storage is needed beyond the size of union value. This function returns true if width is such a width, which case there is no actual need to call those functions. This can be a useful optimization if a large number of union values of such a width are to be initialized or destroyed.

This function returns false if value_init and value_destroy are actually required for the given width.

Function: double value_num (const union value *value)

Returns the numeric value in value, which must have been initialized as a numeric value. Equivalent to value->f.

Function: const char * value_str (const union value *value, int width)
Function: char * value_str_rw (union value *value, int width)

Returns the string value in value, which must have been initialized with positive width width. The string returned is not null-terminated. Only width bytes of returned data may be accessed.

The two different functions exist only for const-correctness. Otherwise they are identical.

It is important that width be the correct value that was passed to value_init. Passing a smaller or larger value (e.g. because that number of bytes will be accessed) will not always work and should be avoided.

Function: void value_copy (union value *dst, const union value *src, int width)

Copies the contents of union value src to dst. Both dst and src must have been initialized with the specified width.

Function: void value_set_missing (union value *value, int width)

Sets value to SYSMIS if it is numeric or to all spaces if it is alphanumeric, according to width. value must have been initialized with the specified width.

Function: bool value_is_resizable (const union value *value, int old_width, int new_width)

Determines whether value, which must have been initialized with the specified old_width, may be resized to new_width. Resizing is possible if the following criteria are met. First, old_width and new_width must be both numeric or both string widths. Second, if new_width is a short string width and less than old_width, resizing is allowed only if bytes new_width through old_width in value contain only spaces.

These rules are part of those used by mv_is_resizable and val_labs_can_set_width.

Function: void value_resize (union value *value, int old_width, int new_width)

Resizes value from old_width to new_width, which must be allowed by the rules stated above. value must have been initialized with the specified old_width before calling this function. After resizing, value has width new_width.

If new_width is greater than old_width, value will be padded on the right with spaces to the new width. If new_width is less than old_width, the rightmost bytes of value are truncated.

Function: bool value_equal (const union value *a, const union value *b, int width)

Compares of a and b, which must both have width width. Returns true if their contents are the same, false if they differ.

Function: int value_compare_3way (const union value *a, const union value *b, int width)

Compares of a and b, which must both have width width. Returns -1 if a is less than b, 0 if they are equal, or 1 if a is greater than b.

Numeric values are compared numerically, with SYSMIS comparing less than any real number. String values are compared lexicographically byte-by-byte.

Function: size_t value_hash (const union value *value, int width, unsigned int basis)

Computes and returns a hash of value, which must have the specified width. The value in basis is folded into the hash.


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2.2 Input and Output Formats

Input and output formats specify how to convert data fields to and from data values (see Input and Output Formats in PSPP Users Guide). PSPP uses struct fmt_spec to represent input and output formats.

Function prototypes and other declarations related to formats are in the <data/format.h> header.

Structure: struct fmt_spec

An input or output format, with the following members:

enum fmt_type type

The format type (see below).

int w

Field width, in bytes. The width of numeric fields is always between 1 and 40 bytes, and the width of string fields is always between 1 and 65534 bytes. However, many individual types of formats place stricter limits on field width (see fmt_max_input_width, fmt_max_output_width).

int d

Number of decimal places, in character positions. For format types that do not allow decimal places to be specified, this value must be 0. Format types that do allow decimal places have type-specific and often width-specific restrictions on d (see fmt_max_input_decimals, fmt_max_output_decimals).

Enumeration: enum fmt_type

An enumerated type representing an input or output format type. Each PSPP input and output format has a corresponding enumeration constant prefixed by ‘FMT’: FMT_F, FMT_COMMA, FMT_DOT, and so on.

The following sections describe functions for manipulating formats and the data in fields represented by formats.


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2.2.1 Constructing and Verifying Formats

These functions construct struct fmt_specs and verify that they are valid.

Function: struct fmt_spec fmt_for_input (enum fmt_type type, int w, int d)
Function: struct fmt_spec fmt_for_output (enum fmt_type type, int w, int d)

Constructs a struct fmt_spec with the given type, w, and d, asserts that the result is a valid input (or output) format, and returns it.

Function: struct fmt_spec fmt_for_output_from_input (const struct fmt_spec *input)

Given input, which must be a valid input format, returns the equivalent output format. See Input and Output Formats in PSPP Users Guide, for the rules for converting input formats into output formats.

Function: struct fmt_spec fmt_default_for_width (int width)

Returns the default output format for a variable of the given width. For a numeric variable, this is F8.2 format; for a string variable, it is the A format of the given width.

The following functions check whether a struct fmt_spec is valid for various uses and return true if so, false otherwise. When any of them returns false, it also outputs an explanatory error message using msg. To suppress error output, enclose a call to one of these functions by a msg_disable/msg_enable pair.

Function: bool fmt_check (const struct fmt_spec *format, bool for_input)
Function: bool fmt_check_input (const struct fmt_spec *format)
Function: bool fmt_check_output (const struct fmt_spec *format)

Checks whether format is a valid input format (for fmt_check_input, or fmt_check if for_input) or output format (for fmt_check_output, or fmt_check if not for_input).

Function: bool fmt_check_type_compat (const struct fmt_spec *format, enum val_type type)

Checks whether format matches the value type type, that is, if type is VAL_NUMERIC and format is a numeric format or type is VAL_STRING and format is a string format.

Function: bool fmt_check_width_compat (const struct fmt_spec *format, int width)

Checks whether format may be used as an output format for a value of the given width.

fmt_var_width, described in the following section, can be also be used to determine the value width needed by a format.


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2.2.2 Format Utility Functions

These functions work with struct fmt_specs.

Function: int fmt_var_width (const struct fmt_spec *format)

Returns the width for values associated with format. If format is a numeric format, the width is 0; if format is an A format, then the width format->w; otherwise, format is an AHEX format and its width is format->w / 2.

Function: char *fmt_to_string (const struct fmt_spec *format, char s[FMT_STRING_LEN_MAX + 1])

Converts format to a human-readable format specifier in s and returns s. format need not be a valid input or output format specifier, e.g. it is allowed to have an excess width or decimal places. In particular, if format has decimals, they are included in the output string, even if format’s type does not allow decimals, to allow accurately presenting incorrect formats to the user.

Function: bool fmt_equal (const struct fmt_spec *a, const struct fmt_spec *b)

Compares a and b memberwise and returns true if they are identical, false otherwise. format need not be a valid input or output format specifier.

Function: void fmt_resize (struct fmt_spec *fmt, int width)

Sets the width of fmt to a valid format for a union value of size width.


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2.2.3 Obtaining Properties of Format Types

These functions work with enum fmt_types instead of the higher-level struct fmt_specs. Their primary purpose is to report properties of each possible format type, which in turn allows clients to abstract away many of the details of the very heterogeneous requirements of each format type.

The first group of functions works with format type names.

Function: const char *fmt_name (enum fmt_type type)

Returns the name for the given type, e.g. "COMMA" for FMT_COMMA.

Function: bool fmt_from_name (const char *name, enum fmt_type *type)

Tries to find the enum fmt_type associated with name. If successful, sets *type to the type and returns true; otherwise, returns false without modifying *type.

The functions below query basic limits on width and decimal places for each kind of format.

Function: bool fmt_takes_decimals (enum fmt_type type)

Returns true if a format of the given type is allowed to have a nonzero number of decimal places (the d member of struct fmt_spec), false if not.

Function: int fmt_min_input_width (enum fmt_type type)
Function: int fmt_max_input_width (enum fmt_type type)
Function: int fmt_min_output_width (enum fmt_type type)
Function: int fmt_max_output_width (enum fmt_type type)

Returns the minimum or maximum width (the w member of struct fmt_spec) allowed for an input or output format of the specified type.

Function: int fmt_max_input_decimals (enum fmt_type type, int width)
Function: int fmt_max_output_decimals (enum fmt_type type, int width)

Returns the maximum number of decimal places allowed for an input or output format, respectively, of the given type and width. Returns 0 if the specified type does not allow any decimal places or if width is too narrow to allow decimal places.

Function: int fmt_step_width (enum fmt_type type)

Returns the “width step” for a struct fmt_spec of the given type. A struct fmt_spec’s width must be a multiple of its type’s width step. Most format types have a width step of 1, so that their formats’ widths may be any integer within the valid range, but hexadecimal numeric formats and AHEX string formats have a width step of 2.

These functions allow clients to broadly determine how each kind of input or output format behaves.

Function: bool fmt_is_string (enum fmt_type type)
Function: bool fmt_is_numeric (enum fmt_type type)

Returns true if type is a format for numeric or string values, respectively, false otherwise.

Function: enum fmt_category fmt_get_category (enum fmt_type type)

Returns the category within which type falls.

Enumeration: enum fmt_category

A group of format types. Format type categories correspond to the input and output categories described in the PSPP user documentation (see Input and Output Formats in PSPP Users Guide).

Each format is in exactly one category. The categories have bitwise disjoint values to make it easy to test whether a format type is in one of multiple categories, e.g.

if (fmt_get_category (type) & (FMT_CAT_DATE | FMT_CAT_TIME))
  {
    /* …type is a date or time format… */
  }

The format categories are:

FMT_CAT_BASIC

Basic numeric formats.

FMT_CAT_CUSTOM

Custom currency formats.

FMT_CAT_LEGACY

Legacy numeric formats.

FMT_CAT_BINARY

Binary formats.

FMT_CAT_HEXADECIMAL

Hexadecimal formats.

FMT_CAT_DATE

Date formats.

FMT_CAT_TIME

Time formats.

FMT_CAT_DATE_COMPONENT

Date component formats.

FMT_CAT_STRING

String formats.

The PSPP input and output routines use the following pair of functions to convert enum fmt_types to and from the separate set of codes used in system and portable files:

Function: int fmt_to_io (enum fmt_type type)

Returns the format code used in system and portable files that corresponds to type.

Function: bool fmt_from_io (int io, enum fmt_type *type)

Converts io, a format code used in system and portable files, into a enum fmt_type in *type. Returns true if successful, false if io is not valid.

These functions reflect the relationship between input and output formats.

Function: enum fmt_type fmt_input_to_output (enum fmt_type type)

Returns the output format type that is used by default by DATA LIST and other input procedures when type is specified as an input format. The conversion from input format to output format is more complicated than simply changing the format. See fmt_for_output_from_input, for a function that performs the entire conversion.

Function: bool fmt_usable_for_input (enum fmt_type type)

Returns true if type may be used as an input format type, false otherwise. The custom currency formats, in particular, may be used for output but not for input.

All format types are valid for output.

The final group of format type property functions obtain human-readable templates that illustrate the formats graphically.

Function: const char *fmt_date_template (enum fmt_type type)

Returns a formatting template for type, which must be a date or time format type. These formats are used by data_in and data_out to guide parsing and formatting date and time data.

Function: char *fmt_dollar_template (const struct fmt_spec *format)

Returns a string of the form $#,###.## according to format, which must be of type FMT_DOLLAR. The caller must free the string with free.


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2.2.4 Numeric Formatting Styles

Each of the basic numeric formats (F, E, COMMA, DOT, DOLLAR, PCT) and custom currency formats (CCA, CCB, CCC, CCD, CCE) has an associated numeric formatting style, represented by struct fmt_number_style. Input and output conversion of formats that have numeric styles is determined mainly by the style, although the formatting rules have special cases that are not represented within the style.

Structure: struct fmt_number_style

A structure type with the following members:

struct substring neg_prefix
struct substring prefix
struct substring suffix
struct substring neg_suffix

A set of strings used a prefix to negative numbers, a prefix to every number, a suffix to every number, and a suffix to negative numbers, respectively. Each of these strings is no more than FMT_STYLE_AFFIX_MAX bytes (currently 16) bytes in length. These strings must be freed with ss_dealloc when no longer needed.

decimal

The character used as a decimal point. It must be either ‘.’ or ‘,’.

grouping

The character used for grouping digits to the left of the decimal point. It may be ‘.’ or ‘,’, in which case it must not be equal to decimal, or it may be set to 0 to disable grouping.

The following functions are provided for working with numeric formatting styles.

Function: void fmt_number_style_init (struct fmt_number_style *style)

Initialises a struct fmt_number_style with all of the prefixes and suffixes set to the empty string, ‘.’ as the decimal point character, and grouping disables.

Function: void fmt_number_style_destroy (struct fmt_number_style *style)

Destroys style, freeing its storage.

Function: struct fmt_number_style *fmt_create (void)

A function which creates an array of all the styles used by pspp, and calls fmt_number_style_init on each of them.

Function: void fmt_done (struct fmt_number_style *styles)

A wrapper function which takes an array of struct fmt_number_style, calls fmt_number_style_destroy on each of them, and then frees the array.

Function: int fmt_affix_width (const struct fmt_number_style *style)

Returns the total length of style’s prefix and suffix.

Function: int fmt_neg_affix_width (const struct fmt_number_style *style)

Returns the total length of style’s neg_prefix and neg_suffix.

PSPP maintains a global set of number styles for each of the basic numeric formats and custom currency formats. The following functions work with these global styles:

Function: const struct fmt_number_style * fmt_get_style (enum fmt_type type)

Returns the numeric style for the given format type.

Function: const char * fmt_name (enum fmt_type type)

Returns the name of the given format type.


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2.2.5 Formatted Data Input and Output

These functions provide the ability to convert data fields into union values and vice versa.

Function: bool data_in (struct substring input, const char *encoding, enum fmt_type type, int implied_decimals, int first_column, const struct dictionary *dict, union value *output, int width)

Parses input as a field containing data in the given format type. The resulting value is stored in output, which the caller must have initialized with the given width. For consistency, width must be 0 if type is a numeric format type and greater than 0 if type is a string format type. encoding should be set to indicate the character encoding of input. dict must be a pointer to the dictionary with which output is associated.

If input is the empty string (with length 0), output is set to the value set on SET BLANKS (see SET BLANKS in PSPP Users Guide) for a numeric value, or to all spaces for a string value. This applies regardless of the usual parsing requirements for type.

If implied_decimals is greater than zero, then the numeric result is shifted right by implied_decimals decimal places if input does not contain a decimal point character or an exponent. Only certain numeric format types support implied decimal places; for string formats and other numeric formats, implied_decimals has no effect. DATA LIST FIXED is the primary user of this feature (see DATA LIST FIXED in PSPP Users Guide). Other callers should generally specify 0 for implied_decimals, to disable this feature.

When input contains invalid input data, data_in outputs a message using msg. If first_column is nonzero, it is included in any such error message as the 1-based column number of the start of the field. The last column in the field is calculated as first_column + input - 1. To suppress error output, enclose the call to data_in by calls to msg_disable and msg_enable.

This function returns true on success, false if a message was output (even if suppressed). Overflow and underflow provoke warnings but are not propagated to the caller as errors.

This function is declared in data/data-in.h.

Function: char * data_out (const union value *input, const struct fmt_spec *format)
Function: char * data_out_legacy (const union value *input, const char *encoding, const struct fmt_spec *format)

Converts the data pointed to by input into a string value, which will be encoded in UTF-8, according to output format specifier format. Format must be a valid output format. The width of input is inferred from format using an algorithm equivalent to fmt_var_width.

When input contains data that cannot be represented in the given format, data_out may output a message using msg, although the current implementation does not consistently do so. To suppress error output, enclose the call to data_out by calls to msg_disable and msg_enable.

This function is declared in data/data-out.h.


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2.3 User-Missing Values

In addition to the system-missing value for numeric values, each variable has a set of user-missing values (see MISSING VALUES in PSPP Users Guide). A set of user-missing values is represented by struct missing_values.

It is rarely necessary to interact directly with a struct missing_values object. Instead, the most common operation, querying whether a particular value is a missing value for a given variable, is most conveniently executed through functions on struct variable. See Variable Missing Values, for details.

A struct missing_values is essentially a set of union values that have a common value width (see Values). For a set of missing values associated with a variable (the common case), the set’s width is the same as the variable’s width.

Function prototypes and other declarations related to missing values are declared in data/missing-values.h.

Structure: struct missing_values

Opaque type that represents a set of missing values.

The contents of a set of missing values is subject to some restrictions. Regardless of width, a set of missing values is allowed to be empty. A set of numeric missing values may contain up to three discrete numeric values, or a range of numeric values (which includes both ends of the range), or a range plus one discrete numeric value. A set of string missing values may contain up to three discrete string values (with the same width as the set), but ranges are not supported.

In addition, values in string missing values wider than MV_MAX_STRING bytes may contain non-space characters only in their first MV_MAX_STRING bytes; all the bytes after the first MV_MAX_STRING must be spaces. See mv_is_acceptable, for a function that tests a value against these constraints.

Macro: int MV_MAX_STRING

Number of bytes in a string missing value that are not required to be spaces. The current value is 8, a value which is fixed by the system file format. In PSPP we could easily eliminate this restriction, but doing so would also require us to extend the system file format in an incompatible way, which we consider a bad tradeoff.

The most often useful functions for missing values are those for testing whether a given value is missing, described in the following section. Several other functions for creating, inspecting, and modifying struct missing_values objects are described afterward, but these functions are much more rarely useful.


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2.3.1 Testing for Missing Values

The most often useful functions for missing values are those for testing whether a given value is missing, described here. However, using one of the corresponding missing value testing functions for variables can be even easier (see Variable Missing Values).

Function: bool mv_is_value_missing (const struct missing_values *mv, const union value *value, enum mv_class class)
Function: bool mv_is_num_missing (const struct missing_values *mv, double value, enum mv_class class)
Function: bool mv_is_str_missing (const struct missing_values *mv, const char value[], enum mv_class class)

Tests whether value is in one of the categories of missing values given by class. Returns true if so, false otherwise.

mv determines the width of value and provides the set of user-missing values to test.

The only difference among these functions in the form in which value is provided, so you may use whichever function is most convenient.

The class argument determines the exact kinds of missing values that the functions test for:

Enumeration: enum mv_class
MV_USER

Returns true if value is in the set of user-missing values given by mv.

MV_SYSTEM

Returns true if value is system-missing. (If mv represents a set of string values, then value is never system-missing.)

MV_ANY
MV_USER | MV_SYSTEM

Returns true if value is user-missing or system-missing.

MV_NONE

Always returns false, that is, value is never considered missing.


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2.3.2 Creation and Destruction

These functions create and destroy struct missing_values objects.

Function: void mv_init (struct missing_values *mv, int width)

Initializes mv as a set of user-missing values. The set is initially empty. Any values added to it must have the specified width.

Function: void mv_destroy (struct missing_values *mv)

Destroys mv, which must not be referred to again.

Function: void mv_copy (struct missing_values *mv, const struct missing_values *old)

Initializes mv as a copy of the existing set of user-missing values old.

Function: void mv_clear (struct missing_values *mv)

Empties the user-missing value set mv, retaining its existing width.


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2.3.3 Changing User-Missing Value Set Width

A few PSPP language constructs copy sets of user-missing values from one variable to another. When the source and target variables have the same width, this is simple. But when the target variable’s width might be different from the source variable’s, it takes a little more work. The functions described here can help.

In fact, it is usually unnecessary to call these functions directly. Most of the time var_set_missing_values, which uses mv_resize internally to resize the new set of missing values to the required width, may be used instead. See var_set_missing_values, for more information.

Function: bool mv_is_resizable (const struct missing_values *mv, int new_width)

Tests whether mv’s width may be changed to new_width using mv_resize. Returns true if it is allowed, false otherwise.

If mv contains any missing values, then it may be resized only if each missing value may be resized, as determined by value_is_resizable (see value_is_resizable).

Function: void mv_resize (struct missing_values *mv, int width)

Changes mv’s width to width. mv and width must satisfy the constraints explained above.

When a string missing value set’s width is increased, each user-missing value is padded on the right with spaces to the new width.


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2.3.4 Inspecting User-Missing Value Sets

These functions inspect the properties and contents of struct missing_values objects.

The first set of functions inspects the discrete values that sets of user-missing values may contain:

Function: bool mv_is_empty (const struct missing_values *mv)

Returns true if mv contains no user-missing values, false if it contains at least one user-missing value (either a discrete value or a numeric range).

Function: int mv_get_width (const struct missing_values *mv)

Returns the width of the user-missing values that mv represents.

Function: int mv_n_values (const struct missing_values *mv)

Returns the number of discrete user-missing values included in mv. The return value will be between 0 and 3. For sets of numeric user-missing values that include a range, the return value will be 0 or 1.

Function: bool mv_has_value (const struct missing_values *mv)

Returns true if mv has at least one discrete user-missing values, that is, if mv_n_values would return nonzero for mv.

Function: const union value * mv_get_value (const struct missing_values *mv, int index)

Returns the discrete user-missing value in mv with the given index. The caller must not modify or free the returned value or refer to it after modifying or freeing mv. The index must be less than the number of discrete user-missing values in mv, as reported by mv_n_values.

The second set of functions inspects the single range of values that numeric sets of user-missing values may contain:

Function: bool mv_has_range (const struct missing_values *mv)

Returns true if mv includes a range, false otherwise.

Function: void mv_get_range (const struct missing_values *mv, double *low, double *high)

Stores the low endpoint of mv’s range in *low and the high endpoint of the range in *high. mv must include a range.


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2.3.5 Modifying User-Missing Value Sets

These functions modify the contents of struct missing_values objects.

The next set of functions applies to all sets of user-missing values:

Function: bool mv_add_value (struct missing_values *mv, const union value *value)
Function: bool mv_add_str (struct missing_values *mv, const char value[])
Function: bool mv_add_num (struct missing_values *mv, double value)

Attempts to add the given discrete value to set of user-missing values mv. value must have the same width as mv. Returns true if value was successfully added, false if the set could not accept any more discrete values or if value is not an acceptable user-missing value (see mv_is_acceptable below).

These functions are equivalent, except for the form in which value is provided, so you may use whichever function is most convenient.

Function: void mv_pop_value (struct missing_values *mv, union value *value)

Removes a discrete value from mv (which must contain at least one discrete value) and stores it in value.

Function: bool mv_replace_value (struct missing_values *mv, const union value *value, int index)

Attempts to replace the discrete value with the given index in mv (which must contain at least index + 1 discrete values) by value. Returns true if successful, false if value is not an acceptable user-missing value (see mv_is_acceptable below).

Function: bool mv_is_acceptable (const union value *value, int width)

Returns true if value, which must have the specified width, may be added to a missing value set of the same width, false if it cannot. As described above, all numeric values and string values of width MV_MAX_STRING or less may be added, but string value of greater width may be added only if bytes beyond the first MV_MAX_STRING are all spaces.

The second set of functions applies only to numeric sets of user-missing values:

Function: bool mv_add_range (struct missing_values *mv, double low, double high)

Attempts to add a numeric range covering lowhigh (inclusive on both ends) to mv, which must be a numeric set of user-missing values. Returns true if the range is successful added, false on failure. Fails if mv already contains a range, or if mv contains more than one discrete value, or if low > high.

Function: void mv_pop_range (struct missing_values *mv, double *low, double *high)

Given mv, which must be a numeric set of user-missing values that contains a range, removes that range from mv and stores its low endpoint in *low and its high endpoint in *high.


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2.4 Value Labels

Each variable has a set of value labels (see VALUE LABELS in PSPP Users Guide), represented as struct val_labs. A struct val_labs is essentially a map from union values to strings. All of the values in a set of value labels have the same width, which for a set of value labels owned by a variable (the common case) is the same as its variable.

Sets of value labels may contain any number of entries.

It is rarely necessary to interact directly with a struct val_labs object. Instead, the most common operation, looking up the label for a value of a given variable, can be conveniently executed through functions on struct variable. See Variable Value Labels, for details.

Function prototypes and other declarations related to missing values are declared in data/value-labels.h.

Structure: struct val_labs

Opaque type that represents a set of value labels.

The most often useful function for value labels is val_labs_find, for looking up the label associated with a value.

Function: char * val_labs_find (const struct val_labs *val_labs, union value value)

Looks in val_labs for a label for the given value. Returns the label, if one is found, or a null pointer otherwise.

Several other functions for working with value labels are described in the following section, but these are more rarely useful.


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2.4.1 Creation and Destruction

These functions create and destroy struct val_labs objects.

Function: struct val_labs * val_labs_create (int width)

Creates and returns an initially empty set of value labels with the given width.

Function: struct val_labs * val_labs_clone (const struct val_labs *val_labs)

Creates and returns a set of value labels whose width and contents are the same as those of var_labs.

Function: void val_labs_clear (struct val_labs *var_labs)

Deletes all value labels from var_labs.

Function: void val_labs_destroy (struct val_labs *var_labs)

Destroys var_labs, which must not be referenced again.


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2.4.2 Value Labels Properties

These functions inspect and manipulate basic properties of struct val_labs objects.

Function: size_t val_labs_count (const struct val_labs *val_labs)

Returns the number of value labels in val_labs.

Function: bool val_labs_can_set_width (const struct val_labs *val_labs, int new_width)

Tests whether val_labs’s width may be changed to new_width using val_labs_set_width. Returns true if it is allowed, false otherwise.

A set of value labels may be resized to a given width only if each value in it may be resized to that width, as determined by value_is_resizable (see value_is_resizable).

Function: void val_labs_set_width (struct val_labs *val_labs, int new_width)

Changes the width of val_labs’s values to new_width, which must be a valid new width as determined by val_labs_can_set_width.


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2.4.3 Adding and Removing Labels

These functions add and remove value labels from a struct val_labs object.

Function: bool val_labs_add (struct val_labs *val_labs, union value value, const char *label)

Adds label to in var_labs as a label for value, which must have the same width as the set of value labels. Returns true if successful, false if value already has a label.

Function: void val_labs_replace (struct val_labs *val_labs, union value value, const char *label)

Adds label to in var_labs as a label for value, which must have the same width as the set of value labels. If value already has a label in var_labs, it is replaced.

Function: bool val_labs_remove (struct val_labs *val_labs, union value value)

Removes from val_labs any label for value, which must have the same width as the set of value labels. Returns true if a label was removed, false otherwise.


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2.4.4 Iterating through Value Labels

These functions allow iteration through the set of value labels represented by a struct val_labs object. They may be used in the context of a for loop:

struct val_labs val_labs;
const struct val_lab *vl;

…

for (vl = val_labs_first (val_labs); vl != NULL;
     vl = val_labs_next (val_labs, vl))
  {
    …do something with vl…
  }

Value labels should not be added or deleted from a struct val_labs as it is undergoing iteration.

Function: const struct val_lab * val_labs_first (const struct val_labs *val_labs)

Returns the first value label in var_labs, if it contains at least one value label, or a null pointer if it does not contain any value labels.

Function: const struct val_lab * val_labs_next (const struct val_labs *val_labs, const struct val_labs_iterator **vl)

Returns the value label in var_labs following vl, if vl is not the last value label in val_labs, or a null pointer if there are no value labels following vl.

Function: const struct val_lab ** val_labs_sorted (const struct val_labs *val_labs)

Allocates and returns an array of pointers to value labels, which are sorted in increasing order by value. The array has val_labs_count (val_labs) elements. The caller is responsible for freeing the array with free (but must not free any of the struct val_lab elements that the array points to).

The iteration functions above work with pointers to struct val_lab which is an opaque data structure that users of struct val_labs must not modify or free directly. The following functions work with objects of this type:

Function: const union value * val_lab_get_value (const struct val_lab *vl)

Returns the value of value label vl. The caller must not modify or free the returned value. (To achieve a similar result, remove the value label with val_labs_remove, then add the new value with val_labs_add.)

The width of the returned value cannot be determined directly from vl. It may be obtained by calling val_labs_get_width on the struct val_labs that vl is in.

Function: const char * val_lab_get_label (const struct val_lab *vl)

Returns the label in vl as a null-terminated string. The caller must not modify or free the returned string. (Use val_labs_replace to change a value label.)


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2.5 Variables

A PSPP variable is represented by struct variable, an opaque type declared in data/variable.h along with related declarations. See Variables in PSPP Users Guide, for a description of PSPP variables from a user perspective.

PSPP is unusual among computer languages in that, by itself, a PSPP variable does not have a value. Instead, a variable in PSPP takes on a value only in the context of a case, which supplies one value for each variable in a set of variables (see Cases). The set of variables in a case, in turn, are ordinarily part of a dictionary (see Dictionaries).

Every variable has several attributes, most of which correspond directly to one of the variable attributes visible to PSPP users (see Attributes in PSPP Users Guide).

The following sections describe variable-related functions and macros.


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2.5.1 Variable Name

A variable name is a string between 1 and ID_MAX_LEN bytes long that satisfies the rules for PSPP identifiers (see Tokens in PSPP Users Guide). Variable names are mixed-case and treated case-insensitively.

Macro: int ID_MAX_LEN

Maximum length of a variable name, in bytes, currently 64.

Only one commonly useful function relates to variable names:

Function: const char * var_get_name (const struct variable *var)

Returns var’s variable name as a C string.

A few other functions are much more rarely used. Some of these functions are used internally by the dictionary implementation:

Function: void var_set_name (struct variable *var, const char *new_name)

Changes the name of var to new_name, which must be a “plausible” name as defined below.

This function cannot be applied to a variable that is part of a dictionary. Use dict_rename_var instead (see Dictionary Renaming Variables).

Function: enum dict_class var_get_dict_class (const struct variable *var)

Returns the dictionary class of var’s name (see Dictionary Class).


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2.5.2 Variable Type and Width

A variable’s type and width are the type and width of its values (see Values).

Function: enum val_type var_get_type (const struct variable *var)

Returns the type of variable var.

Function: int var_get_width (const struct variable *var)

Returns the width of variable var.

Function: void var_set_width (struct variable *var, int width)

Sets the width of variable var to width. The width of a variable should not normally be changed after the variable is created, so this function is rarely used. This function cannot be applied to a variable that is part of a dictionary.

Function: bool var_is_numeric (const struct variable *var)

Returns true if var is a numeric variable, false otherwise.

Function: bool var_is_alpha (const struct variable *var)

Returns true if var is an alphanumeric (string) variable, false otherwise.


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2.5.3 Variable Missing Values

A numeric or short string variable may have a set of user-missing values (see MISSING VALUES in PSPP Users Guide), represented as a struct missing_values (see User-Missing Values).

The most frequent operation on a variable’s missing values is to query whether a value is user- or system-missing:

Function: bool var_is_value_missing (const struct variable *var, const union value *value, enum mv_class class)
Function: bool var_is_num_missing (const struct variable *var, double value, enum mv_class class)
Function: bool var_is_str_missing (const struct variable *var, const char value[], enum mv_class class)

Tests whether value is a missing value of the given class for variable var and returns true if so, false otherwise. var_is_num_missing may only be applied to numeric variables; var_is_str_missing may only be applied to string variables. value must have been initialized with the same width as var.

var_is_type_missing (var, value, class) is equivalent to mv_is_type_missing (var_get_missing_values (var), value, class).

In addition, a few functions are provided to work more directly with a variable’s struct missing_values:

Function: const struct missing_values * var_get_missing_values (const struct variable *var)

Returns the struct missing_values associated with var. The caller must not modify the returned structure. The return value is always non-null.

Function: void var_set_missing_values (struct variable *var, const struct missing_values *miss)

Changes var’s missing values to a copy of miss, or if miss is a null pointer, clears var’s missing values. If miss is non-null, it must have the same width as var or be resizable to var’s width (see mv_resize). The caller retains ownership of miss.

Function: void var_clear_missing_values (struct variable *var)

Clears var’s missing values. Equivalent to var_set_missing_values (var, NULL).

Function: bool var_has_missing_values (const struct variable *var)

Returns true if var has any missing values, false if it has none. Equivalent to mv_is_empty (var_get_missing_values (var)).


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2.5.4 Variable Value Labels

A numeric or short string variable may have a set of value labels (see VALUE LABELS in PSPP Users Guide), represented as a struct val_labs (see Value Labels). The most commonly useful functions for value labels return the value label associated with a value:

Function: const char * var_lookup_value_label (const struct variable *var, const union value *value)

Looks for a label for value in var’s set of value labels. value must have the same width as var. Returns the label if one exists, otherwise a null pointer.

Function: void var_append_value_name (const struct variable *var, const union value *value, struct string *str)

Looks for a label for value in var’s set of value labels. value must have the same width as var. If a label exists, it will be appended to the string pointed to by str. Otherwise, it formats value using var’s print format (see Input and Output Formats) and appends the formatted string.

The underlying struct val_labs structure may also be accessed directly using the functions described below.

Function: bool var_has_value_labels (const struct variable *var)

Returns true if var has at least one value label, false otherwise.

Function: const struct val_labs * var_get_value_labels (const struct variable *var)

Returns the struct val_labs associated with var. If var has no value labels, then the return value may or may not be a null pointer.

The variable retains ownership of the returned struct val_labs, which the caller must not attempt to modify.

Function: void var_set_value_labels (struct variable *var, const struct val_labs *val_labs)

Replaces var’s value labels by a copy of val_labs. The caller retains ownership of val_labs. If val_labs is a null pointer, then var’s value labels, if any, are deleted.

Function: void var_clear_value_labels (struct variable *var)

Deletes var’s value labels. Equivalent to var_set_value_labels (var, NULL).

A final group of functions offers shorthands for operations that would otherwise require getting the value labels from a variable, copying them, modifying them, and then setting the modified value labels into the variable (making a second copy):

Function: bool var_add_value_label (struct variable *var, const union value *value, const char *label)

Attempts to add a copy of label as a label for value for the given var. value must have the same width as var. If value already has a label, then the old label is retained. Returns true if a label is added, false if there was an existing label for value. Either way, the caller retains ownership of value and label.

Function: void var_replace_value_label (struct variable *var, const union value *value, const char *label)

Attempts to add a copy of label as a label for value for the given var. value must have the same width as var. If value already has a label, then label replaces the old label. Either way, the caller retains ownership of value and label.


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2.5.5 Variable Print and Write Formats

Each variable has an associated pair of output formats, called its print format and write format. See Input and Output Formats in PSPP Users Guide, for an introduction to formats. See Input and Output Formats, for a developer’s description of format representation.

The print format is used to convert a variable’s data values to strings for human-readable output. The write format is used similarly for machine-readable output, primarily by the WRITE transformation (see WRITE in PSPP Users Guide). Most often a variable’s print and write formats are the same.

A newly created variable by default has format F8.2 if it is numeric or an A format with the same width as the variable if it is string. Many creators of variables override these defaults.

Both the print format and write format are output formats. Input formats are not part of struct variable. Instead, input programs and transformations keep track of variable input formats themselves.

The following functions work with variable print and write formats.

Function: const struct fmt_spec * var_get_print_format (const struct variable *var)
Function: const struct fmt_spec * var_get_write_format (const struct variable *var)

Returns var’s print or write format, respectively.

Function: void var_set_print_format (struct variable *var, const struct fmt_spec *format)
Function: void var_set_write_format (struct variable *var, const struct fmt_spec *format)
Function: void var_set_both_formats (struct variable *var, const struct fmt_spec *format)

Sets var’s print format, write format, or both formats, respectively, to a copy of format.


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2.5.6 Variable Labels

A variable label is a string that describes a variable. Variable labels may contain spaces and punctuation not allowed in variable names. See VARIABLE LABELS in PSPP Users Guide, for a user-level description of variable labels.

The most commonly useful functions for variable labels are those to retrieve a variable’s label:

Function: const char * var_to_string (const struct variable *var)

Returns var’s variable label, if it has one, otherwise var’s name. In either case the caller must not attempt to modify or free the returned string.

This function is useful for user output.

Function: const char * var_get_label (const struct variable *var)

Returns var’s variable label, if it has one, or a null pointer otherwise.

A few other variable label functions are also provided:

Function: void var_set_label (struct variable *var, const char *label)

Sets var’s variable label to a copy of label, or removes any label from var if label is a null pointer or contains only spaces. Leading and trailing spaces are removed from the variable label and its remaining content is truncated at 255 bytes.

Function: void var_clear_label (struct variable *var)

Removes any variable label from var.

Function: bool var_has_label (const struct variable *var)

Returns true if var has a variable label, false otherwise.


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2.5.7 GUI Attributes

These functions and types access and set attributes that are mainly used by graphical user interfaces. Their values are also stored in and retrieved from system files (but not portable files).

The first group of functions relate to the measurement level of numeric data. New variables are assigned a nominal level of measurement by default.

Enumeration: enum measure

Measurement level. Available values are:

MEASURE_NOMINAL

Numeric data values are arbitrary. Arithmetic operations and numerical comparisons of such data are not meaningful.

MEASURE_ORDINAL

Numeric data values indicate progression along a rank order. Arbitrary arithmetic operations such as addition are not meaningful on such data, but inequality comparisons (less, greater, etc.) have straightforward interpretations.

MEASURE_SCALE

Ratios, sums, etc. of numeric data values have meaningful interpretations.

PSPP does not have a separate category for interval data, which would naturally fall between the ordinal and scale measurement levels.

Function: bool measure_is_valid (enum measure measure)

Returns true if measure is a valid level of measurement, that is, if it is one of the enum measure constants listed above, and false otherwise.

Function: enum measure var_get_measure (const struct variable *var)
Function: void var_set_measure (struct variable *var, enum measure measure)

Gets or sets var’s measurement level.

The following set of functions relates to the width of on-screen columns used for displaying variable data in a graphical user interface environment. The unit of measurement is the width of a character. For proportionally spaced fonts, this is based on the average width of a character.

Function: int var_get_display_width (const struct variable *var)
Function: void var_set_display_width (struct variable *var, int display_width)

Gets or sets var’s display width.

Function: int var_default_display_width (int width)

Returns the default display width for a variable with the given width. The default width of a numeric variable is 8. The default width of a string variable is width or 32, whichever is less.

The final group of functions work with the justification of data when it is displayed in on-screen columns. New variables are by default right-justified.

Enumeration: enum alignment

Text justification. Possible values are ALIGN_LEFT, ALIGN_RIGHT, and ALIGN_CENTRE.

Function: bool alignment_is_valid (enum alignment alignment)

Returns true if alignment is a valid alignment, that is, if it is one of the enum alignment constants listed above, and false otherwise.

Function: enum alignment var_get_alignment (const struct variable *var)
Function: void var_set_alignment (struct variable *var, enum alignment alignment)

Gets or sets var’s alignment.


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2.5.8 Variable Leave Status

Commonly, most or all data in a case come from an input file, read with a command such as DATA LIST or GET, but data can also be generated with transformations such as COMPUTE. In the latter case the question of a datum’s “initial value” can arise. For example, the value of a piece of generated data can recursively depend on its own value:

COMPUTE X = X + 1.

Another situation where the initial value of a variable arises is when its value is not set at all for some cases, e.g. below, Y is set only for the first 10 cases:

DO IF #CASENUM <= 10.
+ COMPUTE Y = 1.
END IF.

By default, the initial value of a datum in either of these situations is the system-missing value for numeric values and spaces for string values. This means that, above, X would be system-missing and that Y would be 1 for the first 10 cases and system-missing for the remainder.

PSPP also supports retaining the value of a variable from one case to another, using the LEAVE command (see LEAVE in PSPP Users Guide). The initial value of such a variable is 0 if it is numeric and spaces if it is a string. If the command ‘LEAVE X Y’ is appended to the above example, then X would have value 1 in the first case and increase by 1 in every succeeding case, and Y would have value 1 for the first 10 cases and 0 for later cases.

The LEAVE command has no effect on data that comes from an input file or whose values do not depend on a variable’s initial value.

The value of scratch variables (see Scratch Variables in PSPP Users Guide) are always left from one case to another.

The following functions work with a variable’s leave status.

Function: bool var_get_leave (const struct variable *var)

Returns true if var’s value is to be retained from case to case, false if it is reinitialized to system-missing or spaces.

Function: void var_set_leave (struct variable *var, bool leave)

If leave is true, marks var to be left from case to case; if leave is false, marks var to be reinitialized for each case.

If var is a scratch variable, leave must be true.

Function: bool var_must_leave (const struct variable *var)

Returns true if var must be left from case to case, that is, if var is a scratch variable.


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2.5.9 Dictionary Class

Occasionally it is useful to classify variables into dictionary classes based on their names. Dictionary classes are represented by enum dict_class. This type and other declarations for dictionary classes are in the <data/dict-class.h> header.

Enumeration: enum dict_class

The dictionary classes are:

DC_ORDINARY

An ordinary variable, one whose name does not begin with ‘$’ or ‘#’.

DC_SYSTEM

A system variable, one whose name begins with ‘$’. See System Variables in PSPP Users Guide.

DC_SCRATCH

A scratch variable, one whose name begins with ‘#’. See Scratch Variables in PSPP Users Guide.

The values for dictionary classes are bitwise disjoint, which allows them to be used in bit-masks. An extra enumeration constant DC_ALL, whose value is the bitwise-or of all of the above constants, is provided to aid in this purpose.

One example use of dictionary classes arises in connection with PSPP syntax that uses a TO b to name the variables in a dictionary from a to b (see Sets of Variables in PSPP Users Guide). This syntax requires a and b to be in the same dictionary class. It limits the variables that it includes to those in that dictionary class.

The following functions relate to dictionary classes.

Function: enum dict_class dict_class_from_id (const char *name)

Returns the “dictionary class” for the given variable name, by looking at its first letter.

Function: const char * dict_class_to_name (enum dict_class dict_class)

Returns a name for the given dict_class as an adjective, e.g. "scratch".

This function should probably not be used in new code as it can lead to difficulties for internationalization.


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2.5.10 Variable Creation and Destruction

Only rarely should PSPP code create or destroy variables directly. Ordinarily, variables are created within a dictionary and destroying by individual deletion from the dictionary or by destroying the entire dictionary at once. The functions here enable the exceptional case, of creation and destruction of variables that are not associated with any dictionary. These functions are used internally in the dictionary implementation.

Function: struct variable * var_create (const char *name, int width)

Creates and returns a new variable with the given name and width. The new variable is not part of any dictionary. Use dict_create_var, instead, to create a variable in a dictionary (see Dictionary Creating Variables).

name should be a valid variable name and must be a “plausible” variable name (see Variable Name). width must be between 0 and MAX_STRING, inclusive (see Values).

The new variable has no user-missing values, value labels, or variable label. Numeric variables initially have F8.2 print and write formats, right-justified display alignment, and scale level of measurement. String variables are created with A print and write formats, left-justified display alignment, and nominal level of measurement. The initial display width is determined by var_default_display_width (see var_default_display_width).

The new variable initially has no short name (see Variable Short Names) and no auxiliary data (see Variable Auxiliary Data).

Function: struct variable * var_clone (const struct variable *old_var)

Creates and returns a new variable with the same attributes as old_var, with a few exceptions. First, the new variable is not part of any dictionary, regardless of whether old_var was in a dictionary. Use dict_clone_var, instead, to add a clone of a variable to a dictionary.

Second, the new variable is not given any short name, even if old_var had a short name. This is because the new variable is likely to be immediately renamed, in which case the short name would be incorrect (see Variable Short Names).

Finally, old_var’s auxiliary data, if any, is not copied to the new variable (see Variable Auxiliary Data).

Function: void var_destroy (struct variable *var)

Destroys var and frees all associated storage, including its auxiliary data, if any. var must not be part of a dictionary. To delete a variable from a dictionary and destroy it, use dict_delete_var (see Dictionary Deleting Variables).


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2.5.11 Variable Short Names

PSPP variable names may be up to 64 (ID_MAX_LEN) bytes long. The system and portable file formats, however, were designed when variable names were limited to 8 bytes in length. Since then, the system file format has been augmented with an extension record that explains how the 8-byte short names map to full-length names (see Long Variable Names Record), but the short names are still present. Thus, the continued presence of the short names is more or less invisible to PSPP users, but every variable in a system file still has a short name that must be unique.

PSPP can generate unique short names for variables based on their full names at the time it creates the data file. If all variables’ full names are unique in their first 8 bytes, then the short names are simply prefixes of the full names; otherwise, PSPP changes them so that they are unique.

By itself this algorithm interoperates well with other software that can read system files, as long as that software understands the extension record that maps short names to long names. When the other software does not understand the extension record, it can produce surprising results. Consider a situation where PSPP reads a system file that contains two variables named RANKINGSCORE, then the user adds a new variable named RANKINGSTATUS, then saves the modified data as a new system file. A program that does not understand long names would then see one of these variables under the name RANKINGS—either one, depending on the algorithm’s details—and the other under a different name. The effect could be very confusing: by adding a new and apparently unrelated variable in PSPP, the user effectively renamed the existing variable.

To counteract this potential problem, every struct variable may have a short name. A variable created by the system or portable file reader receives the short name from that data file. When a variable with a short name is written to a system or portable file, that variable receives priority over other long names whose names begin with the same 8 bytes but which were not read from a data file under that short name.

Variables not created by the system or portable file reader have no short name by default.

A variable with a full name of 8 bytes or less in length has absolute priority for that name when the variable is written to a system file, even over a second variable with that assigned short name.

PSPP does not enforce uniqueness of short names, although the short names read from any given data file will always be unique. If two variables with the same short name are written to a single data file, neither one receives priority.

The following macros and functions relate to short names.

Macro: SHORT_NAME_LEN

Maximum length of a short name, in bytes. Its value is 8.

Function: const char * var_get_short_name (const struct variable *var)

Returns var’s short name, or a null pointer if var has not been assigned a short name.

Function: void var_set_short_name (struct variable *var, const char *short_name)

Sets var’s short name to short_name, or removes var’s short name if short_name is a null pointer. If it is non-null, then short_name must be a plausible name for a variable. The name will be truncated to 8 bytes in length and converted to all-uppercase.

Function: void var_clear_short_name (struct variable *var)

Removes var’s short name.


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2.5.12 Variable Relationships

Variables have close relationships with dictionaries (see Dictionaries) and cases (see Cases). A variable is usually a member of some dictionary, and a case is often used to store data for the set of variables in a dictionary.

These functions report on these relationships. They may be applied only to variables that are in a dictionary.

Function: size_t var_get_dict_index (const struct variable *var)

Returns var’s index within its dictionary. The first variable in a dictionary has index 0, the next variable index 1, and so on.

The dictionary index can be influenced using dictionary functions such as dict_reorder_var (see dict_reorder_var).

Function: size_t var_get_case_index (const struct variable *var)

Returns var’s index within a case. The case index is an index into an array of union value large enough to contain all the data in the dictionary.

The returned case index can be used to access the value of var within a case for its dictionary, as in e.g. case_data_idx (case, var_get_case_index (var)), but ordinarily it is more convenient to use the data access functions that do variable-to-index translation internally, as in e.g. case_data (case, var).


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2.5.13 Variable Auxiliary Data

Each struct variable can have a single pointer to auxiliary data of type void *. These functions manipulate a variable’s auxiliary data.

Use of auxiliary data is discouraged because of its lack of flexibility. Only one client can make use of auxiliary data on a given variable at any time, even though many clients could usefully associate data with a variable.

To prevent multiple clients from attempting to use a variable’s single auxiliary data field at the same time, we adopt the convention that use of auxiliary data in the active dataset dictionary is restricted to the currently executing command. In particular, transformations must not attach auxiliary data to a variable in the active dataset in the expectation that it can be used later when the active dataset is read and the transformation is executed. To help enforce this restriction, auxiliary data is deleted from all variables in the active dataset dictionary after the execution of each PSPP command.

This convention for safe use of auxiliary data applies only to the active dataset dictionary. Rules for other dictionaries may be established separately.

Auxiliary data should be replaced by a more flexible mechanism at some point, but no replacement mechanism has been designed or implemented so far.

The following functions work with variable auxiliary data.

Function: void * var_get_aux (const struct variable *var)

Returns var’s auxiliary data, or a null pointer if none has been assigned.

Function: void * var_attach_aux (const struct variable *var, void *aux, void (*aux_dtor) (struct variable *))

Sets var’s auxiliary data to aux, which must not be null. var must not already have auxiliary data.

Before var’s auxiliary data is cleared by var_clear_aux, aux_dtor, if non-null, will be called with var as its argument. It should free any storage associated with aux, if necessary. var_dtor_free may be appropriate for use as aux_dtor:

Function: void var_dtor_free (struct variable *var)

Frees var’s auxiliary data by calling free.

Function: void var_clear_aux (struct variable *var)

Removes auxiliary data, if any, from var, first calling the destructor passed to var_attach_aux, if one was provided.

Use dict_clear_aux to remove auxiliary data from every variable in a dictionary.

Function: void * var_detach_aux (struct variable *var)

Removes auxiliary data, if any, from var, and returns it. Returns a null pointer if var had no auxiliary data.

Any destructor passed to var_attach_aux is not called, so the caller is responsible for freeing storage associated with the returned auxiliary data.


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2.5.14 Variable Categorical Values

Some statistical procedures require a list of all the values that a categorical variable takes on. Arranging such a list requires making a pass through the data, so PSPP caches categorical values in struct variable.

When variable auxiliary data is revamped to support multiple clients as described in the previous section, categorical values are an obvious candidate. The form in which they are currently supported is inelegant.

Categorical values are not robust against changes in the data. That is, there is currently no way to detect that a transformation has changed data values, meaning that categorical values lists for the changed variables must be recomputed. PSPP is in fact in need of a general-purpose caching and cache-invalidation mechanism, but none has yet been designed and built.

The following functions work with cached categorical values.

Function: struct cat_vals * var_get_obs_vals (const struct variable *var)

Returns var’s set of categorical values. Yields undefined behavior if var does not have any categorical values.

Function: void var_set_obs_vals (const struct variable *var, struct cat_vals *cat_vals)

Destroys var’s categorical values, if any, and replaces them by cat_vals, ownership of which is transferred to var. If cat_vals is a null pointer, then var’s categorical values are cleared.

Function: bool var_has_obs_vals (const struct variable *var)

Returns true if var has a set of categorical values, false otherwise.


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2.6 Dictionaries

Each data file in memory or on disk has an associated dictionary, whose primary purpose is to describe the data in the file. See Variables in PSPP Users Guide, for a PSPP user’s view of a dictionary.

A data file stored in a PSPP format, either as a system or portable file, has a representation of its dictionary embedded in it. Other kinds of data files are usually not self-describing enough to construct a dictionary unassisted, so the dictionaries for these files must be specified explicitly with PSPP commands such as DATA LIST.

The most important content of a dictionary is an array of variables, which must have unique names. A dictionary also conceptually contains a mapping from each of its variables to a location within a case (see Cases), although in fact these mappings are stored within individual variables.

System variables are not members of any dictionary (see System Variables in PSPP Users Guide).

Dictionaries are represented by struct dictionary. Declarations related to dictionaries are in the <data/dictionary.h> header.

The following sections describe functions for use with dictionaries.


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2.6.1 Accessing Variables

The most common operations on a dictionary simply retrieve a struct variable * of an individual variable based on its name or position.

Function: struct variable * dict_lookup_var (const struct dictionary *dict, const char *name)
Function: struct variable * dict_lookup_var_assert (const struct dictionary *dict, const char *name)

Looks up and returns the variable with the given name within dict. Name lookup is not case-sensitive.

dict_lookup_var returns a null pointer if dict does not contain a variable named name. dict_lookup_var_assert asserts that such a variable exists.

Function: struct variable * dict_get_var (const struct dictionary *dict, size_t position)

Returns the variable at the given position in dict. position must be less than the number of variables in dict (see below).

Function: size_t dict_get_var_cnt (const struct dictionary *dict)

Returns the number of variables in dict.

Another pair of functions allows retrieving a number of variables at once. These functions are more rarely useful.

Function: void dict_get_vars (const struct dictionary *dict, const struct variable ***vars, size_t *cnt, enum dict_class exclude)
Function: void dict_get_vars_mutable (const struct dictionary *dict, struct variable ***vars, size_t *cnt, enum dict_class exclude)

Retrieves all of the variables in dict, in their original order, except that any variables in the dictionary classes specified exclude, if any, are excluded (see Dictionary Class). Pointers to the variables are stored in an array allocated with malloc, and a pointer to the first element of this array is stored in *vars. The caller is responsible for freeing this memory when it is no longer needed. The number of variables retrieved is stored in *cnt.

The presence or absence of DC_SYSTEM in exclude has no effect, because dictionaries never include system variables.

One additional function is available. This function is most often used in assertions, but it is not restricted to such use.

Function: bool dict_contains_var (const struct dictionary *dict, const struct variable *var)

Tests whether var is one of the variables in dict. Returns true if so, false otherwise.


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2.6.2 Creating Variables

These functions create a new variable and insert it into a dictionary in a single step.

There is no provision for inserting an already created variable into a dictionary. There is no reason that such a function could not be written, but so far there has been no need for one.

The names provided to one of these functions should be valid variable names and must be plausible variable names.

If a variable with the same name already exists in the dictionary, the non-assert variants of these functions return a null pointer, without modifying the dictionary. The assert variants, on the other hand, assert that no duplicate name exists.

A variable may be in only one dictionary at any given time.

Function: struct variable * dict_create_var (struct dictionary *dict, const char *name, int width)
Function: struct variable * dict_create_var_assert (struct dictionary *dict, const char *name, int width)

Creates a new variable with the given name and width, as if through a call to var_create with those arguments (see var_create), appends the new variable to dict’s array of variables, and returns the new variable.

Function: struct variable * dict_clone_var (struct dictionary *dict, const struct variable *old_var)
Function: struct variable * dict_clone_var_assert (struct dictionary *dict, const struct variable *old_var)

Creates a new variable as a clone of var, inserts the new variable into dict, and returns the new variable. Other properties of the new variable are copied from old_var, except for those not copied by var_clone (see var_clone).

var does not need to be a member of any dictionary.

Function: struct variable * dict_clone_var_as (struct dictionary *dict, const struct variable *old_var, const char *name)
Function: struct variable * dict_clone_var_as_assert (struct dictionary *dict, const struct variable *old_var, const char *name)

These functions are similar to dict_clone_var and dict_clone_var_assert, respectively, except that the new variable is named name instead of keeping old_var’s name.


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2.6.3 Deleting Variables

These functions remove variables from a dictionary’s array of variables. They also destroy the removed variables and free their associated storage.

Deleting a variable to which there might be external pointers is a bad idea. In particular, deleting variables from the active dataset dictionary is a risky proposition, because transformations can retain references to arbitrary variables. Therefore, no variable should be deleted from the active dataset dictionary when any transformations are active, because those transformations might reference the variable to be deleted. The safest time to delete a variable is just after a procedure has been executed, as done by DELETE VARIABLES.

Deleting a variable automatically removes references to that variable from elsewhere in the dictionary as a weighting variable, filter variable, SPLIT FILE variable, or member of a vector.

No functions are provided for removing a variable from a dictionary without destroying that variable. As with insertion of an existing variable, there is no reason that this could not be implemented, but so far there has been no need.

Function: void dict_delete_var (struct dictionary *dict, struct variable *var)

Deletes var from dict, of which it must be a member.

Function: void dict_delete_vars (struct dictionary *dict, struct variable *const *vars, size_t count)

Deletes the count variables in array vars from dict. All of the variables in vars must be members of dict. No variable may be included in vars more than once.

Function: void dict_delete_consecutive_vars (struct dictionary *dict, size_t idx, size_t count)

Deletes the variables in sequential positions idxidx + count (exclusive) from dict, which must contain at least idx + count variables.

Function: void dict_delete_scratch_vars (struct dictionary *dict)

Deletes all scratch variables from dict.


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2.6.4 Changing Variable Order

The variables in a dictionary are stored in an array. These functions change the order of a dictionary’s array of variables without changing which variables are in the dictionary.

Function: void dict_reorder_var (struct dictionary *dict, struct variable *var, size_t new_index)

Moves var, which must be in dict, so that it is at position new_index in dict’s array of variables. Other variables in dict, if any, retain their relative positions. new_index must be less than the number of variables in dict.

Function: void dict_reorder_vars (struct dictionary *dict, struct variable *const *new_order, size_t count)

Moves the count variables in new_order to the beginning of dict’s array of variables in the specified order. Other variables in dict, if any, retain their relative positions.

All of the variables in new_order must be in dict. No duplicates are allowed within new_order, which means that count must be no greater than the number of variables in dict.


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2.6.5 Renaming Variables

These functions change the names of variables within a dictionary. The var_set_name function (see var_set_name) cannot be applied directly to a variable that is in a dictionary, because struct dictionary contains an index by name that var_set_name would not update. The following functions take care to update the index as well. They also ensure that variable renaming does not cause a dictionary to contain a duplicate variable name.

Function: void dict_rename_var (struct dictionary *dict, struct variable *var, const char *new_name)

Changes the name of var, which must be in dict, to new_name. A variable named new_name must not already be in dict, unless new_name is the same as var’s current name.

Function: bool dict_rename_vars (struct dictionary *dicT, struct variable **vars, char **new_names, size_t count, char **err_name)

Renames each of the count variables in vars to the name in the corresponding position of new_names. If the renaming would result in a duplicate variable name, returns false and stores one of the names that would be be duplicated into *err_name, if err_name is non-null. Otherwise, the renaming is successful, and true is returned.


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2.6.6 Weight Variable

A data set’s cases may optionally be weighted by the value of a numeric variable. See WEIGHT in PSPP Users Guide, for a user view of weight variables.

The weight variable is written to and read from system and portable files.

The most commonly useful function related to weighting is a convenience function to retrieve a weighting value from a case.

Function: double dict_get_case_weight (const struct dictionary *dict, const struct ccase *case, bool *warn_on_invalid)

Retrieves and returns the value of the weighting variable specified by dict from case. Returns 1.0 if dict has no weighting variable.

Returns 0.0 if c’s weight value is user- or system-missing, zero, or negative. In such a case, if warn_on_invalid is non-null and *warn_on_invalid is true, dict_get_case_weight also issues an error message and sets *warn_on_invalid to false. To disable error reporting, pass a null pointer or a pointer to false as warn_on_invalid or use a msg_disable/msg_enable pair.

The dictionary also has a pair of functions for getting and setting the weight variable.

Function: struct variable * dict_get_weight (const struct dictionary *dict)

Returns dict’s current weighting variable, or a null pointer if the dictionary does not have a weighting variable.

Function: void dict_set_weight (struct dictionary *dict, struct variable *var)

Sets dict’s weighting variable to var. If var is non-null, it must be a numeric variable in dict. If var is null, then dict’s weighting variable, if any, is cleared.


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2.6.7 Filter Variable

When the active dataset is read by a procedure, cases can be excluded from analysis based on the values of a filter variable. See FILTER in PSPP Users Guide, for a user view of filtering.

These functions store and retrieve the filter variable. They are rarely useful, because the data analysis framework automatically excludes from analysis the cases that should be filtered.

Function: struct variable * dict_get_filter (const struct dictionary *dict)

Returns dict’s current filter variable, or a null pointer if the dictionary does not have a filter variable.

Function: void dict_set_filter (struct dictionary *dict, struct variable *var)

Sets dict’s filter variable to var. If var is non-null, it must be a numeric variable in dict. If var is null, then dict’s filter variable, if any, is cleared.


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2.6.8 Case Limit

The limit on cases analyzed by a procedure, set by the N OF CASES command (see N OF CASES in PSPP Users Guide), is stored as part of the dictionary. The dictionary does not, on the other hand, play any role in enforcing the case limit (a job done by data analysis framework code).

A case limit of 0 means that the number of cases is not limited.

These functions are rarely useful, because the data analysis framework automatically excludes from analysis any cases beyond the limit.

Function: casenumber dict_get_case_limit (const struct dictionary *dict)

Returns the current case limit for dict.

Function: void dict_set_case_limit (struct dictionary *dict, casenumber limit)

Sets dict’s case limit to limit.


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2.6.9 Split Variables

The user may use the SPLIT FILE command (see SPLIT FILE in PSPP Users Guide) to select a set of variables on which to split the active dataset into groups of cases to be analyzed independently in each statistical procedure. The set of split variables is stored as part of the dictionary, although the effect on data analysis is implemented by each individual statistical procedure.

Split variables may be numeric or short or long string variables.

The most useful functions for split variables are those to retrieve them. Even these functions are rarely useful directly: for the purpose of breaking cases into groups based on the values of the split variables, it is usually easier to use casegrouper_create_splits.

Function: const struct variable *const * dict_get_split_vars (const struct dictionary *dict)

Returns a pointer to an array of pointers to split variables. If and only if there are no split variables, returns a null pointer. The caller must not modify or free the returned array.

Function: size_t dict_get_split_cnt (const struct dictionary *dict)

Returns the number of split variables.

The following functions are also available for working with split variables.

Function: void dict_set_split_vars (struct dictionary *dict, struct variable *const *vars, size_t cnt)

Sets dict’s split variables to the cnt variables in vars. If cnt is 0, then dict will not have any split variables. The caller retains ownership of vars.

Function: void dict_unset_split_var (struct dictionary *dict, struct variable *var)

Removes var, which must be a variable in dict, from dict’s split of split variables.


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2.6.10 File Label

A dictionary may optionally have an associated string that describes its contents, called its file label. The user may set the file label with the FILE LABEL command (see FILE LABEL in PSPP Users Guide).

These functions set and retrieve the file label.

Function: const char * dict_get_label (const struct dictionary *dict)

Returns dict’s file label. If dict does not have a label, returns a null pointer.

Function: void dict_set_label (struct dictionary *dict, const char *label)

Sets dict’s label to label. If label is non-null, then its content, truncated to at most 60 bytes, becomes the new file label. If label is null, then dict’s label is removed.

The caller retains ownership of label.


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2.6.11 Documents

A dictionary may include an arbitrary number of lines of explanatory text, called the dictionary’s documents. For compatibility, document lines have a fixed width, and lines that are not exactly this width are truncated or padded with spaces as necessary to bring them to the correct width.

PSPP users can use the DOCUMENT (see DOCUMENT in PSPP Users Guide), ADD DOCUMENT (see ADD DOCUMENT in PSPP Users Guide), and DROP DOCUMENTS (see DROP DOCUMENTS in PSPP Users Guide) commands to manipulate documents.

Macro: int DOC_LINE_LENGTH

The fixed length of a document line, in bytes, defined to 80.

The following functions work with whole sets of documents. They accept or return sets of documents formatted as null-terminated strings that are an exact multiple of DOC_LINE_LENGTH bytes in length.

Function: const char * dict_get_documents (const struct dictionary *dict)

Returns the documents in dict, or a null pointer if dict has no documents.

Function: void dict_set_documents (struct dictionary *dict, const char *new_documents)

Sets dict’s documents to new_documents. If new_documents is a null pointer or an empty string, then dict’s documents are cleared. The caller retains ownership of new_documents.

Function: void dict_clear_documents (struct dictionary *dict)

Clears the documents from dict.

The following functions work with individual lines in a dictionary’s set of documents.

Function: void dict_add_document_line (struct dictionary *dict, const char *content)

Appends content to the documents in dict. The text in content will be truncated or padded with spaces as necessary to make it exactly DOC_LINE_LENGTH bytes long. The caller retains ownership of content.

If content is over DOC_LINE_LENGTH, this function also issues a warning using msg. To suppress the warning, enclose a call to one of this function in a msg_disable/msg_enable pair.

Function: size_t dict_get_document_line_cnt (const struct dictionary *dict)

Returns the number of line of documents in dict. If the dictionary contains no documents, returns 0.

Function: void dict_get_document_line (const struct dictionary *dict, size_t idx, struct string *content)

Replaces the text in content (which must already have been initialized by the caller) by the document line in dict numbered idx, which must be less than the number of lines of documents in dict. Any trailing white space in the document line is trimmed, so that content will have a length between 0 and DOC_LINE_LENGTH.


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2.7 Coding Conventions

Every .c file should have ‘#include <config.h>’ as its first non-comment line. No .h file should include config.h.

This section needs to be finished.


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2.8 Cases

This section needs to be written.


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2.9 Data Sets

This section needs to be written.


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2.10 Pools

This section needs to be written.


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3 Parsing Command Syntax


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4 Processing Data

Developer’s Guide

Proposed outline:

* Introduction
* Basic concepts
** Data sets
** Variables
** Dictionaries
** Coding conventions
** Pools
* Syntax parsing
* Data processing
** Reading data
*** Casereaders generalities
*** Casereaders from data files
*** Casereaders from the active dataset
*** Other casereaders
** Writing data
*** Casewriters generally
*** Casewriters to data files
*** Modifying the active dataset
**** Modifying cases obtained from active dataset casereaders has no real effect
**** Transformations; procedures that transform
** Transforming data
*** Sorting and merging
*** Filtering
*** Grouping
**** Ordering and interaction of filtering and grouping
*** Multiple passes over data
*** Counting cases and case weights
** Best practices
*** Multiple passes with filters versus single pass with loops
*** Sequential versus random access
*** Managing memory
*** Passing cases around
*** Renaming casereaders
*** Avoiding excessive buffering
*** Propagating errors
*** Avoid static/global data
*** Don't worry about null filters, groups, etc.
*** Be aware of reference counting semantics for cases

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5 Presenting Output


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6 Internationalisation

Internationalisation in pspp is complicated. The most annoying aspect is that of character-encoding. This chapter attempts to describe the problems and current ways in which they are addressed.

6.1 The working locales

Pspp has three “working” locales:

Each of these locales may, at different times take separate (or identical) values. So for example, a French statistician can use pspp to prepare a report in the English language, using a datafile which has been created by a Japanese researcher hence uses a Japanese character set.

It’s rarely, if ever, necessary to interrogate the system to find out the values of the 3 locales. However it’s important to be aware of the source (destination) locale when reading (writing) string data. When transfering data between a source and a destination, the appropriate recoding must be performed.

6.1.1 The user interface locale

This is the locale which is visible to the person using pspp. Error messages and confidence indications are written in this locale. For example “Cannot open file” will be written in the user interface locale.

This locale is set from the environment of the user who starts pspp{ire} or from the system locale if not set.

6.1.2 The output locale

This locale is the one that should be visible to the person reading a report generated by pspp. Non-data related strings (Eg: “Page number”, “Standard Deviation” etc.) will appear in this locale.

6.1.3 The data locale

This locale is the one associated with the data being analysed with pspp. The only important aspect of this locale is the character encoding. 1 The dictionary pertaining to the data contains a field denoting the encoding. Any string data stored in a union value will be encoded in the dictionary’s character set.

6.2 System files

*.sav files contain a field which is supposed to identify the encoding of the data they contain (see Machine Integer Info Record). However, many files produced by early versions of spss set this to “2” (ASCII) regardless of the encoding of the data. Later versions contain an additional record (see Character Encoding Record) describing the encoding. When a system file is read, the dictionary’s encoding is set using information gleened from the system file. If the encoding cannot be determined or would be unreliable, then it remains unset.

6.3 GUI

The psppire graphic user interface is written using the Gtk+ api, for which all strings must be encoded in UTF8. All strings passed to the GTK+/GLib library functions (except for filenames) must be UTF-8 encoded otherwise errors will occur. Thus, for the purposes of the programming psppire, the user interface locale should be assumed to be UTF8, even if setlocale and/or nl_langinfo indicates otherwise.

6.3.1 Filenames

The GLib API has some special functions for dealing with filenames. Strings returned from functions like gtk_file_chooser_dialog_get_name are not, in general, encoded in UTF8, but in “filename” encoding. If that filename is passed to another GLib function which expects a filename, no conversion is necessary. If it’s passed to a function for the purposes of displaying it (eg. in a window’s title-bar) it must be converted to UTF8 — there is a special function for this: g_filename_display_name or g_filename_basename. If however, a filename needs to be passed outside of GTK+/GLib (for example to fopen) it must be converted to the local system encoding.

6.4 Existing locale handling functions

The major aspect of locale handling which the programmer has to consider is that of character encoding.

The following function is used to recode strings:

Function: char * recode_string (const char *to, const char *from, const char *text, int len);

Converts the string text, which is encoded in from to a new string encoded in to encoding. If len is not -1, then it must be the number of bytes in text. It is the caller’s responsibility to free the returned string when no longer required.

In order to minimise the number of conversions required, and to simplify design, PSPP attempts to store all internal strings in UTF8 encoding. Thus, when reading system and portable files (or any other data source), the following items are immediately converted to UTF8 encoding:

Conversely, when writing system files, these are converted back to the encoding of that system file.

String data stored in union values are left in their original encoding. These will be converted by the data_in/data_out functions.

6.5 Quirks

For historical reasons, not all locale handling follows posix conventions. This makes it difficult (impossible?) to elegantly handle the issues. For example, it would make sense for the gui’s datasheet to display numbers formatted according to the LC_NUMERIC category of the data locale. Instead however there is the data_out function (see Obtaining Properties of Format Types) which uses the settings_get_decimal_char function instead of the decimal separator of the locale. Similarly, formatting of monetary values is displayed in a pspp/spss specific fashion instead of using the LC_MONETARY category.


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7 Function Index

Jump to:   *  
A   C   D   F   H   I   L   M   S   V  
Index Entry  Section

*
*: Formatted Data Input and Output
*: Formatted Data Input and Output
*: Internationalisation
*fmt_create: Numeric Formatting Styles
*fmt_dollar_template: Obtaining Properties of Format Types
*fmt_to_string: Format Utility Functions

A
alignment: Variable GUI Attributes
alignment_is_valid: Variable GUI Attributes

C
char: Obtaining Properties of Format Types
char: Obtaining Properties of Format Types

D
data_in: Formatted Data Input and Output
dict_add_document_line: Dictionary Documents
dict_class_from_id: Dictionary Class
dict_class_to_name: Dictionary Class
dict_clear_documents: Dictionary Documents
dict_clone_var: Dictionary Creating Variables
dict_clone_var_as: Dictionary Creating Variables
dict_clone_var_assert: Dictionary Creating Variables
dict_clone_var_as_assert: Dictionary Creating Variables
dict_contains_var: Dictionary Variable Access
dict_create_var: Dictionary Creating Variables
dict_create_var_assert: Dictionary Creating Variables
dict_delete_consecutive_vars: Dictionary Deleting Variables
dict_delete_scratch_vars: Dictionary Deleting Variables
dict_delete_var: Dictionary Deleting Variables
dict_delete_vars: Dictionary Deleting Variables
dict_get_case_limit: Dictionary Case Limit
dict_get_case_weight: Dictionary Weight Variable
dict_get_documents: Dictionary Documents
dict_get_document_line: Dictionary Documents
dict_get_document_line_cnt: Dictionary Documents
dict_get_filter: Dictionary Filter Variable
dict_get_label: Dictionary File Label
dict_get_split_cnt: Dictionary Split Variables
dict_get_split_vars: Dictionary Split Variables
dict_get_var: Dictionary Variable Access
dict_get_vars: Dictionary Variable Access
dict_get_vars_mutable: Dictionary Variable Access
dict_get_var_cnt: Dictionary Variable Access
dict_get_weight: Dictionary Weight Variable
dict_lookup_var: Dictionary Variable Access
dict_lookup_var_assert: Dictionary Variable Access
dict_rename_var: Dictionary Renaming Variables
dict_rename_vars: Dictionary Renaming Variables
dict_reorder_var: Dictionary Reordering Variables
dict_reorder_vars: Dictionary Reordering Variables
dict_set_case_limit: Dictionary Case Limit
dict_set_documents: Dictionary Documents
dict_set_filter: Dictionary Filter Variable
dict_set_label: Dictionary File Label
dict_set_split_vars: Dictionary Split Variables
dict_set_weight: Dictionary Weight Variable
dict_unset_split_var: Dictionary Split Variables
DOC_LINE_LENGTH: Dictionary Documents

F
fmt_affix_width: Numeric Formatting Styles
fmt_category: Obtaining Properties of Format Types
fmt_check: Constructing and Verifying Formats
fmt_check_input: Constructing and Verifying Formats
fmt_check_output: Constructing and Verifying Formats
fmt_check_type_compat: Constructing and Verifying Formats
fmt_check_width_compat: Constructing and Verifying Formats
fmt_default_for_width: Constructing and Verifying Formats
fmt_done: Numeric Formatting Styles
fmt_equal: Format Utility Functions
fmt_for_input: Constructing and Verifying Formats
fmt_for_output: Constructing and Verifying Formats
fmt_for_output_from_input: Constructing and Verifying Formats
fmt_from_io: Obtaining Properties of Format Types
fmt_from_name: Obtaining Properties of Format Types
fmt_get_style: Numeric Formatting Styles
fmt_is_numeric: Obtaining Properties of Format Types
fmt_is_string: Obtaining Properties of Format Types
fmt_max_input_decimals: Obtaining Properties of Format Types
fmt_max_input_width: Obtaining Properties of Format Types
fmt_max_output_decimals: Obtaining Properties of Format Types
fmt_max_output_width: Obtaining Properties of Format Types
fmt_min_input_width: Obtaining Properties of Format Types
fmt_min_output_width: Obtaining Properties of Format Types
fmt_name: Numeric Formatting Styles
fmt_neg_affix_width: Numeric Formatting Styles
fmt_number_style_destroy: Numeric Formatting Styles
fmt_number_style_init: Numeric Formatting Styles
fmt_resize: Format Utility Functions
fmt_step_width: Obtaining Properties of Format Types
fmt_takes_decimals: Obtaining Properties of Format Types
fmt_to_io: Obtaining Properties of Format Types
fmt_type: Obtaining Properties of Format Types
fmt_usable_for_input: Obtaining Properties of Format Types
fmt_var_width: Format Utility Functions

H
HIGHEST: Numeric Values

I
ID_MAX_LEN: Variable Name

L
LOWEST: Numeric Values

M
MAX_STRING: Values
measure: Variable GUI Attributes
measure_is_valid: Variable GUI Attributes
mv_add_num: Modifying User-Missing Value Sets
mv_add_range: Modifying User-Missing Value Sets
mv_add_str: Modifying User-Missing Value Sets
mv_add_value: Modifying User-Missing Value Sets
mv_clear: Creating and Destroying User-Missing Values
mv_copy: Creating and Destroying User-Missing Values
mv_destroy: Creating and Destroying User-Missing Values
mv_get_range: Inspecting User-Missing Value Sets
mv_get_value: Inspecting User-Missing Value Sets
mv_get_width: Inspecting User-Missing Value Sets
mv_has_range: Inspecting User-Missing Value Sets
mv_has_value: Inspecting User-Missing Value Sets
mv_init: Creating and Destroying User-Missing Values
mv_is_acceptable: Modifying User-Missing Value Sets
mv_is_empty: Inspecting User-Missing Value Sets
mv_is_num_missing: Testing for Missing Values
mv_is_resizable: Changing User-Missing Value Set Width
mv_is_str_missing: Testing for Missing Values
mv_is_value_missing: Testing for Missing Values
MV_MAX_STRING: User-Missing Values
mv_n_values: Inspecting User-Missing Value Sets
mv_pop_range: Modifying User-Missing Value Sets
mv_pop_value: Modifying User-Missing Value Sets
mv_replace_value: Modifying User-Missing Value Sets
mv_resize: Changing User-Missing Value Set Width

S
SHORT_NAME_LEN: Variable Short Names
SYSMIS: Numeric Values

V
value_compare_3way: Runtime Typed Values
value_copy: Runtime Typed Values
value_destroy: Runtime Typed Values
value_equal: Runtime Typed Values
value_hash: Runtime Typed Values
value_init: Runtime Typed Values
value_is_resizable: Runtime Typed Values
value_needs_init: Runtime Typed Values
value_num: Runtime Typed Values
value_resize: Runtime Typed Values
value_set_missing: Runtime Typed Values
value_str: Runtime Typed Values
value_str_rw: Runtime Typed Values
val_labs_add: Value Labels Adding and Removing Labels
val_labs_can_set_width: Value Labels Properties
val_labs_clear: Value Labels Creation and Destruction
val_labs_clone: Value Labels Creation and Destruction
val_labs_count: Value Labels Properties
val_labs_create: Value Labels Creation and Destruction
val_labs_destroy: Value Labels Creation and Destruction
val_labs_find: Value Labels
val_labs_first: Value Labels Iteration
val_labs_next: Value Labels Iteration
val_labs_remove: Value Labels Adding and Removing Labels
val_labs_replace: Value Labels Adding and Removing Labels
val_labs_set_width: Value Labels Properties
val_labs_sorted: Value Labels Iteration
val_lab_get_label: Value Labels Iteration
val_lab_get_value: Value Labels Iteration
val_type_from_width: Values
val_type_is_valid: Values
var_add_value_label: Variable Value Labels
var_append_value_name: Variable Value Labels
var_attach_aux: Variable Auxiliary Data
var_clear_aux: Variable Auxiliary Data
var_clear_label: Variable Labels
var_clear_missing_values: Variable Missing Values
var_clear_short_name: Variable Short Names
var_clear_value_labels: Variable Value Labels
var_clone: Variable Creation and Destruction
var_create: Variable Creation and Destruction
var_default_display_width: Variable GUI Attributes
var_destroy: Variable Creation and Destruction
var_detach_aux: Variable Auxiliary Data
var_get_aux: Variable Auxiliary Data
var_get_case_index: Variable Relationships
var_get_dict_class: Variable Name
var_get_dict_index: Variable Relationships
var_get_display_width: Variable GUI Attributes
var_get_label: Variable Labels
var_get_leave: Variable Leave Status
var_get_missing_values: Variable Missing Values
var_get_name: Variable Name
var_get_obs_vals: Variable Categorical Values
var_get_print_format: Variable Print and Write Formats
var_get_short_name: Variable Short Names
var_get_type: Variable Type and Width
var_get_value_labels: Variable Value Labels
var_get_width: Variable Type and Width
var_get_write_format: Variable Print and Write Formats
var_has_label: Variable Labels
var_has_missing_values: Variable Missing Values
var_has_obs_vals: Variable Categorical Values
var_has_value_labels: Variable Value Labels
var_is_alpha: Variable Type and Width
var_is_numeric: Variable Type and Width
var_is_num_missing: Variable Missing Values
var_is_str_missing: Variable Missing Values
var_is_value_missing: Variable Missing Values
var_lookup_value_label: Variable Value Labels
var_must_leave: Variable Leave Status
var_replace_value_label: Variable Value Labels
var_set_alignment: Variable GUI Attributes
var_set_both_formats: Variable Print and Write Formats
var_set_display_width: Variable GUI Attributes
var_set_label: Variable Labels
var_set_leave: Variable Leave Status
var_set_measure: Variable GUI Attributes
var_set_missing_values: Variable Missing Values
var_set_name: Variable Name
var_set_obs_vals: Variable Categorical Values
var_set_print_format: Variable Print and Write Formats
var_set_short_name: Variable Short Names
var_set_value_labels: Variable Value Labels
var_set_width: Variable Type and Width
var_set_write_format: Variable Print and Write Formats
var_to_string: Variable Labels
void: Variable Auxiliary Data

Jump to:   *  
A   C   D   F   H   I   L   M   S   V  

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8 Concept Index

Jump to:   M   N   S   V   W  
Index Entry  Section

M
MAX_STRING: Values
MAX_STRING: String Values

N
numeric value: Values

S
string value: Values

V
value: Values

W
width: Values

Jump to:   M   N   S   V   W  

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Appendix A Portable File Format

These days, most computers use the same internal data formats for integer and floating-point data, if one ignores little differences like big- versus little-endian byte ordering. However, occasionally it is necessary to exchange data between systems with incompatible data formats. This is what portable files are designed to do.

Please note: This information is gleaned from examination of ASCII-formatted portable files only, so some of it may be incorrect for portable files formatted in EBCDIC or other character sets.


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A.1 Portable File Characters

Portable files are arranged as a series of lines of 80 characters each. Each line is terminated by a carriage-return, line-feed sequence (“new-lines”). New-lines are only used to avoid line length limits imposed by some OSes; they are not meaningful.

Most lines in portable files are exactly 80 characters long. The only exception is a line that ends in one or more spaces, in which the spaces may optionally be omitted. Thus, a portable file reader must act as though a line shorter than 80 characters is padded to that length with spaces.

The file must be terminated with a ‘Z’ character. In addition, if the final line in the file does not have exactly 80 characters, then it is padded on the right with ‘Z’ characters. (The file contents may be in any character set; the file contains a description of its own character set, as explained in the next section. Therefore, the ‘Z’ character is not necessarily an ASCII ‘Z’.)

For the rest of the description of the portable file format, new-lines and the trailing ‘Z’s will be ignored, as if they did not exist, because they are not an important part of understanding the file contents.


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A.2 Portable File Structure

Every portable file consists of the following records, in sequence:

Most records are identified by a single-character tag code. The file header and version info record do not have a tag.

Other than these single-character codes, there are three types of fields in a portable file: floating-point, integer, and string. Floating-point fields have the following format:

Integer fields take a form identical to floating-point fields, but they may not contain a fraction.

String fields take the form of a integer field having value n, followed by exactly n characters, which are the string content.


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A.3 Portable File Header

Every portable file begins with a 464-byte header, consisting of a 200-byte collection of vanity splash strings, followed by a 256-byte character set translation table, followed by an 8-byte tag string.

The 200-byte segment is divided into five 40-byte sections, each of which represents the string charset SPSS PORT FILE in a different character set encoding, where charset is the name of the character set used in the file, e.g. ASCII or EBCDIC. Each string is padded on the right with spaces in its respective character set.

It appears that these strings exist only to inform those who might view the file on a screen, and that they are not parsed by SPSS products. Thus, they can be safely ignored. For those interested, the strings are supposed to be in the following character sets, in the specified order: EBCDIC, 7-bit ASCII, CDC 6-bit ASCII, 6-bit ASCII, Honeywell 6-bit ASCII.

The 256-byte segment describes a mapping from the character set used in the portable file to an arbitrary character set having characters at the following positions:

0–60

Control characters. Not important enough to describe in full here.

61–63

Reserved.

64–73

Digits ‘0’ through ‘9’.

74–99

Capital letters ‘A’ through ‘Z’.

100–125

Lowercase letters ‘a’ through ‘z’.

126

Space.

127–130

Symbols .<(+

131

Solid vertical pipe.

132–142

Symbols &[]!$*);^-/

143

Broken vertical pipe.

144–150

Symbols ,%_>?`:

151

British pound symbol.

152–155

Symbols @'=".

156

Less than or equal symbol.

157

Empty box.

158

Plus or minus.

159

Filled box.

160

Degree symbol.

161

Dagger.

162

Symbol ‘~’.

163

En dash.

164

Lower left corner box draw.

165

Upper left corner box draw.

166

Greater than or equal symbol.

167–176

Superscript ‘0’ through ‘9’.

177

Lower right corner box draw.

178

Upper right corner box draw.

179

Not equal symbol.

180

Em dash.

181

Superscript ‘(’.

182

Superscript ‘)’.

183

Horizontal dagger (?).

184–186

Symbols ‘{}\’.

187

Cents symbol.

188

Centered dot, or bullet.

189–255

Reserved.

Symbols that are not defined in a particular character set are set to the same value as symbol 64; i.e., to ‘0’.

The 8-byte tag string consists of the exact characters SPSSPORT in the portable file’s character set, which can be used to verify that the file is indeed a portable file.


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A.4 Version and Date Info Record

This record does not have a tag code. It has the following structure:


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A.5 Identification Records

The product identification record has tag code ‘1’. It consists of a single string field giving the name of the product that wrote the portable file.

The author identification record has tag code ‘2’. It is optional. If present, it consists of a single string field giving the name of the person who caused the portable file to be written.

The subproduct identification record has tag code ‘3’. It is optional. If present, it consists of a single string field giving additional information on the product that wrote the portable file.


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A.6 Variable Count Record

The variable count record has tag code ‘4’. It consists of a single integer field giving the number of variables in the file dictionary.


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A.7 Precision Record

The precision record has tag code ‘5’. It consists of a single integer field specifying the maximum number of base-30 digits used in data in the file.


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A.8 Case Weight Variable Record

The case weight variable record is optional. If it is present, it indicates the variable used for weighting cases; if it is absent, cases are unweighted. It has tag code ‘6’. It consists of a single string field that names the weighting variable.


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A.9 Variable Records

Each variable record represents a single variable. Variable records have tag code ‘7’. They have the following structure:

Each variable record can optionally be followed by a missing value record, which has tag code ‘8’. A missing value record has one field, the missing value itself (a floating-point or string, as appropriate). Up to three of these missing value records can be used.

There is also a record for missing value ranges, which has tag code ‘B’. It is followed by two fields representing the range, which are floating-point or string as appropriate. If a missing value range is present, it may be followed by a single missing value record.

Tag codes ‘9’ and ‘A’ represent LO THRU x and x THRU HI ranges, respectively. Each is followed by a single field representing x. If one of the ranges is present, it may be followed by a single missing value record.

In addition, each variable record can optionally be followed by a variable label record, which has tag code ‘C’. A variable label record has one field, the variable label itself (string).


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A.10 Value Label Records

Value label records have tag code ‘D’. They have the following format:

A few portable files that specify duplicate value labels, that is, two different labels for a single value of a single variable, have been spotted in the wild. PSPP uses the last value label specified in these cases.


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A.11 Document Record

One document record may optionally follow the value label record. The document record consists of tag code ‘E’, following by the number of document lines as an integer, followed by that number of strings, each of which represents one document line. Document lines must be 80 bytes long or shorter.


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A.12 Portable File Data

The data record has tag code ‘F’. There is only one tag for all the data; thus, all the data must follow the dictionary. The data is terminated by the end-of-file marker ‘Z’, which is not valid as the beginning of a data element.

Data elements are output in the same order as the variable records describing them. String variables are output as string fields, and numeric variables are output as floating-point fields.


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Appendix B System File Format

A system file encapsulates a set of cases and dictionary information that describes how they may be interpreted. This chapter describes the format of a system file.

System files use four data types: 8-bit characters, 32-bit integers, 64-bit integers, and 64-bit floating points, called here char, int32, int64, and flt64, respectively. Data is not necessarily aligned on a word or double-word boundary: the long variable name record (see Long Variable Names Record) and very long string records (see Very Long String Record) have arbitrary byte length and can therefore cause all data coming after them in the file to be misaligned.

Integer data in system files may be big-endian or little-endian. A reader may detect the endianness of a system file by examining layout_code in the file header record (see layout_code).

Floating-point data in system files may nominally be in IEEE 754, IBM, or VAX formats. A reader may detect the floating-point format in use by examining bias in the file header record (see bias).

PSPP detects big-endian and little-endian integer formats in system files and translates as necessary. PSPP also detects the floating-point format in use, as well as the endianness of IEEE 754 floating-point numbers, and translates as needed. However, only IEEE 754 numbers with the same endianness as integer data in the same file have actually been observed in system files, and it is likely that other formats are obsolete or were never used.

System files use a few floating point values for special purposes:

SYSMIS

The system-missing value is represented by the largest possible negative number in the floating point format (-DBL_MAX).

HIGHEST

HIGHEST is used as the high end of a missing value range with an unbounded maximum. It is represented by the largest possible positive number (DBL_MAX).

LOWEST

LOWEST is used as the low end of a missing value range with an unbounded minimum. It was originally represented by the second-largest negative number (in IEEE 754 format, 0xffeffffffffffffe). System files written by SPSS 21 and later instead use the largest negative number (-DBL_MAX), the same value as SYSMIS. This does not lead to ambiguity because LOWEST appears in system files only in missing value ranges, which never contain SYSMIS.

System files may use most character encodings based on an 8-bit unit. UTF-16 and UTF-32, based on wider units, appear to be unacceptable. rec_type in the file header record is sufficient to distinguish between ASCII and EBCDIC based encodings. The best way to determine the specific encoding in use is to consult the character encoding record (see Character Encoding Record), if present, and failing that the character_code in the machine integer info record (see Machine Integer Info Record). The same encoding should be used for the dictionary and the data in the file, although it is possible to artificially synthesize files that use different encodings (see Character Encoding Record).


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B.1 System File Record Structure

System files are divided into records with the following format:

int32               type;
char                data[];

This header does not identify the length of the data or any information about what it contains, so the system file reader must understand the format of data based on type. However, records with type 7, called extension records, have a stricter format:

int32               type;
int32               subtype;
int32               size;
int32               count;
char                data[size * count];
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. This value identifies a particular kind of extension record.

int32 size;

The size of each piece of data that follows the header, in bytes. Known extension records use 1, 4, or 8, for char, int32, and flt64 format data, respectively.

int32 count;

The number of pieces of data that follow the header.

char data[size * count];

Data, whose format and interpretation depend on the subtype.

An extension record contains exactly size * count bytes of data, which allows a reader that does not understand an extension record to skip it. Extension records provide only nonessential information, so this allows for files written by newer software to preserve backward compatibility with older or less capable readers.

Records in a system file must appear in the following order:

We advise authors of programs that read system files to tolerate format variations. Various kinds of misformatting and corruption have been observed in system files written by SPSS and other software alike. In particular, because extension records provide nonessential information, it is generally better to ignore an extension record entirely than to refuse to read a system file.

The following sections describe the known kinds of records.


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B.2 File Header Record

A system file begins with the file header, with the following format:

char                rec_type[4];
char                prod_name[60];
int32               layout_code;
int32               nominal_case_size;
int32               compression;
int32               weight_index;
int32               ncases;
flt64               bias;
char                creation_date[9];
char                creation_time[8];
char                file_label[64];
char                padding[3];
char rec_type[4];

Record type code, either ‘$FL2’ for system files with uncompressed data or data compressed with simple bytecode compression, or ‘$FL3’ for system files with ZLIB compressed data.

This is truly a character field that uses the character encoding as other strings. Thus, in a file with an ASCII-based character encoding this field contains 24 46 4c 32 or 24 46 4c 33, and in a file with an EBCDIC-based encoding this field contains 5b c6 d3 f2. (No EBCDIC-based ZLIB-compressed files have been observed.)

char prod_name[60];

Product identification string. This always begins with the characters ‘@(#) SPSS DATA FILE’. PSPP uses the remaining characters to give its version and the operating system name; for example, ‘GNU pspp 0.1.4 - sparc-sun-solaris2.5.2’. The string is truncated if it would be longer than 60 characters; otherwise it is padded on the right with spaces.

int32 layout_code;

Normally set to 2, although a few system files have been spotted in the wild with a value of 3 here. PSPP use this value to determine the file’s integer endianness (see System File Format).

int32 nominal_case_size;

Number of data elements per case. This is the number of variables, except that long string variables add extra data elements (one for every 8 characters after the first 8). However, string variables do not contribute to this value beyond the first 255 bytes. Further, system files written by some systems set this value to -1. In general, it is unsafe for systems reading system files to rely upon this value.

int32 compression;

Set to 0 if the data in the file is not compressed, 1 if the data is compressed with simple bytecode compression, 2 if the data is ZLIB compressed. This field has value 2 if and only if rec_type is ‘$FL3’.

int32 weight_index;

If one of the variables in the data set is used as a weighting variable, set to the dictionary index of that variable, plus 1 (see Dictionary Index). Otherwise, set to 0.

int32 ncases;

Set to the number of cases in the file if it is known, or -1 otherwise.

In the general case it is not possible to determine the number of cases that will be output to a system file at the time that the header is written. The way that this is dealt with is by writing the entire system file, including the header, then seeking back to the beginning of the file and writing just the ncases field. For files in which this is not valid, the seek operation fails. In this case, ncases remains -1.

flt64 bias;

Compression bias, ordinarily set to 100. Only integers between 1 - bias and 251 - bias can be compressed.

By assuming that its value is 100, PSPP uses bias to determine the file’s floating-point format and endianness (see System File Format). If the compression bias is not 100, PSPP cannot auto-detect the floating-point format and assumes that it is IEEE 754 format with the same endianness as the system file’s integers, which is correct for all known system files.

char creation_date[9];

Date of creation of the system file, in ‘dd mmm yy’ format, with the month as standard English abbreviations, using an initial capital letter and following with lowercase. If the date is not available then this field is arbitrarily set to ‘01 Jan 70’.

char creation_time[8];

Time of creation of the system file, in ‘hh:mm:ss’ format and using 24-hour time. If the time is not available then this field is arbitrarily set to ‘00:00:00’.

char file_label[64];

File label declared by the user, if any (see FILE LABEL in PSPP Users Guide). Padded on the right with spaces.

A product that identifies itself as VOXCO INTERVIEWER 4.3 uses CR-only line ends in this field, rather than the more usual LF-only or CR LF line ends.

char padding[3];

Ignored padding bytes to make the structure a multiple of 32 bits in length. Set to zeros.


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B.3 Variable Record

There must be one variable record for each numeric variable and each string variable with width 8 bytes or less. String variables wider than 8 bytes have one variable record for each 8 bytes, rounding up. The first variable record for a long string specifies the variable’s correct dictionary information. Subsequent variable records for a long string are filled with dummy information: a type of -1, no variable label or missing values, print and write formats that are ignored, and an empty string as name. A few system files have been encountered that include a variable label on dummy variable records, so readers should take care to parse dummy variable records in the same way as other variable records.

The dictionary index of a variable is its offset in the set of variable records, including dummy variable records for long string variables. The first variable record has a dictionary index of 0, the second has a dictionary index of 1, and so on.

The system file format does not directly support string variables wider than 255 bytes. Such very long string variables are represented by a number of narrower string variables. See Very Long String Record, for details.

A system file should contain at least one variable and thus at least one variable record, but system files have been observed in the wild without any variables (thus, no data either).

int32               rec_type;
int32               type;
int32               has_var_label;
int32               n_missing_values;
int32               print;
int32               write;
char                name[8];

/* Present only if has_var_label is 1. */
int32               label_len;
char                label[];

/* Present only if n_missing_values is nonzero. */
flt64               missing_values[];
int32 rec_type;

Record type code. Always set to 2.

int32 type;

Variable type code. Set to 0 for a numeric variable. For a short string variable or the first part of a long string variable, this is set to the width of the string. For the second and subsequent parts of a long string variable, set to -1, and the remaining fields in the structure are ignored.

int32 has_var_label;

If this variable has a variable label, set to 1; otherwise, set to 0.

int32 n_missing_values;

If the variable has no missing values, set to 0. If the variable has one, two, or three discrete missing values, set to 1, 2, or 3, respectively. If the variable has a range for missing variables, set to -2; if the variable has a range for missing variables plus a single discrete value, set to -3.

A long string variable always has the value 0 here. A separate record indicates missing values for long string variables (see Long String Missing Values Record).

int32 print;

Print format for this variable. See below.

int32 write;

Write format for this variable. See below.

char name[8];

Variable name. The variable name must begin with a capital letter or the at-sign (‘@’). Subsequent characters may also be digits, octothorpes (‘#’), dollar signs (‘$’), underscores (‘_’), or full stops (‘.’). The variable name is padded on the right with spaces.

The ‘name’ fields should be unique within a system file. System files written by SPSS that contain very long string variables with similar names sometimes contain duplicate names that are later eliminated by resolving the very long string names (see Very Long String Record). PSPP handles duplicates by assigning them new, unique names.

int32 label_len;

This field is present only if has_var_label is set to 1. It is set to the length, in characters, of the variable label. The documented maximum length varies from 120 to 255 based on SPSS version, but some files have been seen with longer labels. PSPP accepts labels of any length.

char label[];

This field is present only if has_var_label is set to 1. It has length label_len, rounded up to the nearest multiple of 32 bits. The first label_len characters are the variable’s variable label.

flt64 missing_values[];

This field is present only if n_missing_values is nonzero. It has the same number of 8-byte elements as the absolute value of n_missing_values. Each element is interpreted as a number for numeric variables (with HIGHEST and LOWEST indicated as described in the chapter introduction). For string variables of width less than 8 bytes, elements are right-padded with spaces; for string variables wider than 8 bytes, only the first 8 bytes of each missing value are specified, with the remainder implicitly all spaces.

For discrete missing values, each element represents one missing value. When a range is present, the first element denotes the minimum value in the range, and the second element denotes the maximum value in the range. When a range plus a value are present, the third element denotes the additional discrete missing value.

The print and write members of sysfile_variable are output formats coded into int32 types. The least-significant byte of the int32 represents the number of decimal places, and the next two bytes in order of increasing significance represent field width and format type, respectively. The most-significant byte is not used and should be set to zero.

Format types are defined as follows:

ValueMeaning
0Not used.
1A
2AHEX
3COMMA
4DOLLAR
5F
6IB
7PIBHEX
8P
9PIB
10PK
11RB
12RBHEX
13Not used.
14Not used.
15Z
16N
17E
18Not used.
19Not used.
20DATE
21TIME
22DATETIME
23ADATE
24JDATE
25DTIME
26WKDAY
27MONTH
28MOYR
29QYR
30WKYR
31PCT
32DOT
33CCA
34CCB
35CCC
36CCD
37CCE
38EDATE
39SDATE

A few system files have been observed in the wild with invalid write fields, in particular with value 0. Readers should probably treat invalid print or write fields as some default format.


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B.4 Value Labels Records

The value label records documented in this section are used for numeric and short string variables only. Long string variables may have value labels, but their value labels are recorded using a different record type (see Long String Value Labels Record).

The value label record has the following format:

int32               rec_type;
int32               label_count;

/* Repeated label_cnt times. */
char                value[8];
char                label_len;
char                label[];
int32 rec_type;

Record type. Always set to 3.

int32 label_count;

Number of value labels present in this record.

The remaining fields are repeated count times. Each repetition specifies one value label.

char value[8];

A numeric value or a short string value padded as necessary to 8 bytes in length. Its type and width cannot be determined until the following value label variables record (see below) is read.

char label_len;

The label’s length, in bytes. The documented maximum length varies from 60 to 120 based on SPSS version. PSPP supports value labels up to 255 bytes long.

char label[];

label_len bytes of the actual label, followed by up to 7 bytes of padding to bring label and label_len together to a multiple of 8 bytes in length.

The value label record is always immediately followed by a value label variables record with the following format:

int32               rec_type;
int32               var_count;
int32               vars[];
int32 rec_type;

Record type. Always set to 4.

int32 var_count;

Number of variables that the associated value labels from the value label record are to be applied.

int32 vars[];

A list of dictionary indexes of variables to which to apply the value labels (see Dictionary Index). There are var_count elements.

String variables wider than 8 bytes may not be specified in this list.


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B.5 Document Record

The document record, if present, has the following format:

int32               rec_type;
int32               n_lines;
char                lines[][80];
int32 rec_type;

Record type. Always set to 6.

int32 n_lines;

Number of lines of documents present.

char lines[][80];

Document lines. The number of elements is defined by n_lines. Lines shorter than 80 characters are padded on the right with spaces.


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B.6 Machine Integer Info Record

The integer info record, if present, has the following format:

/* Header. */
int32               rec_type;
int32               subtype;
int32               size;
int32               count;

/* Data. */
int32               version_major;
int32               version_minor;
int32               version_revision;
int32               machine_code;
int32               floating_point_rep;
int32               compression_code;
int32               endianness;
int32               character_code;
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Always set to 3.

int32 size;

Size of each piece of data in the data part, in bytes. Always set to 4.

int32 count;

Number of pieces of data in the data part. Always set to 8.

int32 version_major;

PSPP major version number. In version x.y.z, this is x.

int32 version_minor;

PSPP minor version number. In version x.y.z, this is y.

int32 version_revision;

PSPP version revision number. In version x.y.z, this is z.

int32 machine_code;

Machine code. PSPP always set this field to value to -1, but other values may appear.

int32 floating_point_rep;

Floating point representation code. For IEEE 754 systems this is 1. IBM 370 sets this to 2, and DEC VAX E to 3.

int32 compression_code;

Compression code. Always set to 1, regardless of whether or how the file is compressed.

int32 endianness;

Machine endianness. 1 indicates big-endian, 2 indicates little-endian.

int32 character_code;

Character code. The following values have been actually observed in system files:

1

EBCDIC.

2

7-bit ASCII.

1250

The windows-1250 code page for Central European and Eastern European languages.

1252

The windows-1252 code page for Western European languages.

28591

ISO 8859-1.

65001

UTF-8.

The following additional values are known to be defined:

3

8-bit “ASCII”.

4

DEC Kanji.

Other Windows code page numbers are known to be generally valid.

Old versions of SPSS for Unix and Windows always wrote value 2 in this field, regardless of the encoding in use. Newer versions also write the character encoding as a string (see Character Encoding Record).


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B.7 Machine Floating-Point Info Record

The floating-point info record, if present, has the following format:

/* Header. */
int32               rec_type;
int32               subtype;
int32               size;
int32               count;

/* Data. */
flt64               sysmis;
flt64               highest;
flt64               lowest;
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Always set to 4.

int32 size;

Size of each piece of data in the data part, in bytes. Always set to 8.

int32 count;

Number of pieces of data in the data part. Always set to 3.

flt64 sysmis;
flt64 highest;
flt64 lowest;

The system missing value, the value used for HIGHEST in missing values, and the value used for LOWEST in missing values, respectively. See System File Format, for more information.

The SPSSWriter library in PHP, which identifies itself as FOM SPSS 1.0.0 in the file header record prod_name field, writes unexpected values to these fields, but it uses the same values consistently throughout the rest of the file.


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B.8 Multiple Response Sets Records

The system file format has two different types of records that represent multiple response sets (see MRSETS in PSPP Users Guide). The first type of record describes multiple response sets that can be understood by SPSS before version 14. The second type of record, with a closely related format, is used for multiple dichotomy sets that use the CATEGORYLABELS=COUNTEDVALUES feature added in version 14.

/* Header. */
int32               rec_type;
int32               subtype;
int32               size;
int32               count;

/* Exactly count bytes of data. */
char                mrsets[];
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Set to 7 for records that describe multiple response sets understood by SPSS before version 14, or to 19 for records that describe dichotomy sets that use the CATEGORYLABELS=COUNTEDVALUES feature added in version 14.

int32 size;

The size of each element in the mrsets member. Always set to 1.

int32 count;

The total number of bytes in mrsets.

char mrsets[];

Zero or more line feeds (byte 0x0a), followed by a series of multiple response sets, each of which consists of the following:

Example: Given appropriate variable definitions, consider the following MRSETS command:

MRSETS /MCGROUP NAME=$a LABEL='my mcgroup' VARIABLES=a b c
       /MDGROUP NAME=$b VARIABLES=g e f d VALUE=55
       /MDGROUP NAME=$c LABEL='mdgroup #2' VARIABLES=h i j VALUE='Yes'
       /MDGROUP NAME=$d LABEL='third mdgroup' CATEGORYLABELS=COUNTEDVALUES
        VARIABLES=k l m VALUE=34
       /MDGROUP NAME=$e CATEGORYLABELS=COUNTEDVALUES LABELSOURCE=VARLABEL
        VARIABLES=n o p VALUE='choice'.

The above would generate the following multiple response set record of subtype 7:

$a=C 10 my mcgroup a b c
$b=D2 55 0  g e f d
$c=D3 Yes 10 mdgroup #2 h i j

It would also generate the following multiple response set record with subtype 19:

$d=E 1 2 34 13 third mdgroup k l m
$e=E 11 6 choice 0  n o p

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B.9 Extra Product Info Record

This optional record appears to contain a text string that describes the program that wrote the file and the source of the data. (This is redundant with the file label and product info found in the file header record.)

/* Header. */
int32               rec_type;
int32               subtype;
int32               size;
int32               count;

/* Exactly count bytes of data. */
char                info[];
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Always set to 10.

int32 size;

The size of each element in the info member. Always set to 1.

int32 count;

The total number of bytes in info.

char info[];

A text string. A product that identifies itself as VOXCO INTERVIEWER 4.3 uses CR-only line ends in this field, rather than the more usual LF-only or CR LF line ends.


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B.10 Variable Display Parameter Record

The variable display parameter record, if present, has the following format:

/* Header. */
int32               rec_type;
int32               subtype;
int32               size;
int32               count;

/* Repeated count times. */
int32               measure;
int32               width;           /* Not always present. */
int32               alignment;
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Always set to 11.

int32 size;

The size of int32. Always set to 4.

int32 count;

The number of sets of variable display parameters (ordinarily the number of variables in the dictionary), times 2 or 3.

The remaining members are repeated count times, in the same order as the variable records. No element corresponds to variable records that continue long string variables. The meanings of these members are as follows:

int32 measure;

The measurement type of the variable:

1

Nominal Scale

2

Ordinal Scale

3

Continuous Scale

SPSS sometimes writes a measure of 0. PSPP interprets this as nominal scale.

int32 width;

The width of the display column for the variable in characters.

This field is present if count is 3 times the number of variables in the dictionary. It is omitted if count is 2 times the number of variables.

int32 alignment;

The alignment of the variable for display purposes:

0

Left aligned

1

Right aligned

2

Centre aligned


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B.11 Long Variable Names Record

If present, the long variable names record has the following format:

/* Header. */
int32               rec_type;
int32               subtype;
int32               size;
int32               count;

/* Exactly count bytes of data. */
char                var_name_pairs[];
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Always set to 13.

int32 size;

The size of each element in the var_name_pairs member. Always set to 1.

int32 count;

The total number of bytes in var_name_pairs.

char var_name_pairs[];

A list of keyvalue tuples, where key is the name of a variable, and value is its long variable name. The key field is at most 8 bytes long and must match the name of a variable which appears in the variable record (see Variable Record). The value field is at most 64 bytes long. The key and value fields are separated by a ‘=’ byte. Each tuple is separated by a byte whose value is 09. There is no trailing separator following the last tuple. The total length is count bytes.


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B.12 Very Long String Record

Old versions of SPSS limited string variables to a width of 255 bytes. For backward compatibility with these older versions, the system file format represents a string longer than 255 bytes, called a very long string, as a collection of strings no longer than 255 bytes each. The strings concatenated to make a very long string are called its segments; for consistency, variables other than very long strings are considered to have a single segment.

A very long string with a width of w has n = (w + 251) / 252 segments, that is, one segment for every 252 bytes of width, rounding up. It would be logical, then, for each of the segments except the last to have a width of 252 and the last segment to have the remainder, but this is not the case. In fact, each segment except the last has a width of 255 bytes. The last segment has width w - (n - 1) * 252; some versions of SPSS make it slightly wider, but not wide enough to make the last segment require another 8 bytes of data.

Data is packed tightly into segments of a very long string, 255 bytes per segment. Because 255 bytes of segment data are allocated for every 252 bytes of the very long string’s width (approximately), some unused space is left over at the end of the allocated segments. Data in unused space is ignored.

Example: Consider a very long string of width 20,000. Such a very long string has 20,000 / 252 = 80 (rounding up) segments. The first 79 segments have width 255; the last segment has width 20,000 - 79 * 252 = 92 or slightly wider (up to 96 bytes, the next multiple of 8). The very long string’s data is actually stored in the 19,890 bytes in the first 78 segments, plus the first 110 bytes of the 79th segment (19,890 + 110 = 20,000). The remaining 145 bytes of the 79th segment and all 92 bytes of the 80th segment are unused.

The very long string record explains how to stitch together segments to obtain very long string data. For each of the very long string variables in the dictionary, it specifies the name of its first segment’s variable and the very long string variable’s actual width. The remaining segments immediately follow the named variable in the system file’s dictionary.

The very long string record, which is present only if the system file contains very long string variables, has the following format:

/* Header. */
int32               rec_type;
int32               subtype;
int32               size;
int32               count;

/* Exactly count bytes of data. */
char                string_lengths[];
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Always set to 14.

int32 size;

The size of each element in the string_lengths member. Always set to 1.

int32 count;

The total number of bytes in string_lengths.

char string_lengths[];

A list of keyvalue tuples, where key is the name of a variable, and value is its length. The key field is at most 8 bytes long and must match the name of a variable which appears in the variable record (see Variable Record). The value field is exactly 5 bytes long. It is a zero-padded, ASCII-encoded string that is the length of the variable. The key and value fields are separated by a ‘=’ byte. Tuples are delimited by a two-byte sequence {00, 09}. After the last tuple, there may be a single byte 00, or {00, 09}. The total length is count bytes.


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B.13 Character Encoding Record

This record, if present, indicates the character encoding for string data, long variable names, variable labels, value labels and other strings in the file.

/* Header. */
int32               rec_type;
int32               subtype;
int32               size;
int32               count;

/* Exactly count bytes of data. */
char                encoding[];
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Always set to 20.

int32 size;

The size of each element in the encoding member. Always set to 1.

int32 count;

The total number of bytes in encoding.

char encoding[];

The name of the character encoding. Normally this will be an official IANA character set name or alias. See http://www.iana.org/assignments/character-sets. Character set names are not case-sensitive, but SPSS appears to write them in all-uppercase.

This record is not present in files generated by older software. See also the character_code field in the machine integer info record (see character-code).

When the character encoding record and the machine integer info record are both present, all system files observed in practice indicate the same character encoding, e.g. 1252 as character_code and windows-1252 as encoding, 65001 and UTF-8, etc.

If, for testing purposes, a file is crafted with different character_code and encoding, it seems that character_code controls the encoding for all strings in the system file before the dictionary termination record, including strings in data (e.g. string missing values), and encoding controls the encoding for strings following the dictionary termination record.


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B.14 Long String Value Labels Record

This record, if present, specifies value labels for long string variables.

/* Header. */
int32               rec_type;
int32               subtype;
int32               size;
int32               count;

/* Repeated up to exactly count bytes. */
int32               var_name_len;
char                var_name[];
int32               var_width;
int32               n_labels;
long_string_label   labels[];
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Always set to 21.

int32 size;

Always set to 1.

int32 count;

The number of bytes following the header until the next header.

int32 var_name_len;
char var_name[];

The number of bytes in the name of the variable that has long string value labels, plus the variable name itself, which consists of exactly var_name_len bytes. The variable name is not padded to any particular boundary, nor is it null-terminated.

int32 var_width;

The width of the variable, in bytes, which will be between 9 and 32767.

int32 n_labels;
long_string_label labels[];

The long string labels themselves. The labels array contains exactly n_labels elements, each of which has the following substructure:

int32               value_len;
char                value[];
int32               label_len;
char                label[];
int32 value_len;
char value[];

The string value being labeled. value_len is the number of bytes in value; it is equal to var_width. The value array is not padded or null-terminated.

int32 label_len;
char label[];

The label for the string value. label_len, which must be between 0 and 120, is the number of bytes in label. The label array is not padded or null-terminated.


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B.15 Long String Missing Values Record

This record, if present, specifies missing values for long string variables.

/* Header. */
int32               rec_type;
int32               subtype;
int32               size;
int32               count;

/* Repeated up to exactly count bytes. */
int32               var_name_len;
char                var_name[];
char                n_missing_values;
long_string_missing_value   values[];
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Always set to 22.

int32 size;

Always set to 1.

int32 count;

The number of bytes following the header until the next header.

int32 var_name_len;
char var_name[];

The number of bytes in the name of the long string variable that has missing values, plus the variable name itself, which consists of exactly var_name_len bytes. The variable name is not padded to any particular boundary, nor is it null-terminated.

char n_missing_values;

The number of missing values, either 1, 2, or 3. (This is, unusually, a single byte instead of a 32-bit number.)

long_string_missing_value values[];

The missing values themselves. This array contains exactly n_missing_values elements, each of which has the following substructure:

int32               value_len;
char                value[];
int32 value_len;

The length of the missing value string, in bytes. This value should be 8, because long string variables are at least 8 bytes wide (by definition), only the first 8 bytes of a long string variable’s missing values are allowed to be non-spaces, and any spaces within the first 8 bytes are included in the missing value here.

char value[];

The missing value string, exactly value_len bytes, without any padding or null terminator.


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B.16 Data File and Variable Attributes Records

The data file and variable attributes records represent custom attributes for the system file or for individual variables in the system file, as defined on the DATAFILE ATTRIBUTE (see DATAFILE ATTRIBUTE in PSPP Users Guide) and VARIABLE ATTRIBUTE commands (see VARIABLE ATTRIBUTE in PSPP Users Guide), respectively.

/* Header. */
int32               rec_type;
int32               subtype;
int32               size;
int32               count;

/* Exactly count bytes of data. */
char                attributes[];
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Always set to 17 for a data file attribute record or to 18 for a variable attributes record.

int32 size;

The size of each element in the attributes member. Always set to 1.

int32 count;

The total number of bytes in attributes.

char attributes[];

The attributes, in a text-based format.

In record subtype 17, this field contains a single attribute set. An attribute set is a sequence of one or more attributes concatenated together. Each attribute consists of a name, which has the same syntax as a variable name, followed by, inside parentheses, a sequence of one or more values. Each value consists of a string enclosed in single quotes (') followed by a line feed (byte 0x0a). A value may contain single quote characters, which are not themselves escaped or quoted or required to be present in pairs. There is no apparent way to embed a line feed in a value. There is no distinction between an attribute with a single value and an attribute array with one element.

In record subtype 18, this field contains a sequence of one or more variable attribute sets. If more than one variable attribute set is present, each one after the first is delimited from the previous by /. Each variable attribute set consists of a long variable name, followed by :, followed by an attribute set with the same syntax as on record subtype 17.

System files written by Stata 14.1/-savespss- 1.77 by S.Radyakin may include multiple records with subtype 18, one per variable that has variable attributes.

The total length is count bytes.

Example

A system file produced with the following VARIABLE ATTRIBUTE commands in effect:

VARIABLE ATTRIBUTE VARIABLES=dummy ATTRIBUTE=fred[1]('23') fred[2]('34').
VARIABLE ATTRIBUTE VARIABLES=dummy ATTRIBUTE=bert('123').

will contain a variable attribute record with the following contents:

0000  07 00 00 00 12 00 00 00  01 00 00 00 22 00 00 00  |............"...|
0010  64 75 6d 6d 79 3a 66 72  65 64 28 27 32 33 27 0a  |dummy:fred('23'.|
0020  27 33 34 27 0a 29 62 65  72 74 28 27 31 32 33 27  |'34'.)bert('123'|
0030  0a 29                                             |.)              |

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B.16.1 Variable Roles

A variable’s role is represented as an attribute named $@Role. This attribute has a single element whose values and their meanings are:

0

Input. This, the default, is the most common role.

1

Output.

2

Both.

3

None.

4

Partition.

5

Split.


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B.17 Extended Number of Cases Record

The file header record expresses the number of cases in the system file as an int32 (see File Header Record). This record allows the number of cases in the system file to be expressed as a 64-bit number.

int32               rec_type;
int32               subtype;
int32               size;
int32               count;
int64               unknown;
int64               ncases64;
int32 rec_type;

Record type. Always set to 7.

int32 subtype;

Record subtype. Always set to 16.

int32 size;

Size of each element. Always set to 8.

int32 count;

Number of pieces of data in the data part. Alway set to 2.

int64 unknown;

Meaning unknown. Always set to 1.

int64 ncases64;

Number of cases in the file as a 64-bit integer. Presumably this could be -1 to indicate that the number of cases is unknown, for the same reason as ncases in the file header record, but this has not been observed in the wild.


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B.18 Other Informational Records

This chapter documents many specific types of extension records are documented here, but others are known to exist. PSPP ignores unknown extension records when reading system files.

The following extension record subtypes have also been observed, with the following believed meanings:

5

A set of grouped variables (according to Aapi Hämäläinen).

6

Date info, probably related to USE (according to Aapi Hämäläinen).

12

A UUID in the format described in RFC 4122. Only two examples observed, both written by SPSS 13, and in each case the UUID contained both upper and lower case.

24

XML that describes how data in the file should be displayed on-screen.


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B.19 Dictionary Termination Record

The dictionary termination record separates all other records from the data records.

int32               rec_type;
int32               filler;
int32 rec_type;

Record type. Always set to 999.

int32 filler;

Ignored padding. Should be set to 0.


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B.20 Data Record

The data record must follow all other records in the system file. Every system file must have a data record that specifies data for at least one case. The format of the data record varies depending on the value of compression in the file header record:

0: no compression

Data is arranged as a series of 8-byte elements. Each element corresponds to the variable declared in the respective variable record (see Variable Record). Numeric values are given in flt64 format; string values are literal characters string, padded on the right when necessary to fill out 8-byte units.

1: bytecode compression

The first 8 bytes of the data record is divided into a series of 1-byte command codes. These codes have meanings as described below:

0

Ignored. If the program writing the system file accumulates compressed data in blocks of fixed length, 0 bytes can be used to pad out extra bytes remaining at the end of a fixed-size block.

1 through 251

A number with value code - bias, where code is the value of the compression code and bias is the variable bias from the file header. For example, code 105 with bias 100.0 (the normal value) indicates a numeric variable of value 5. One file has been seen written by SPSS 14 that contained such a code in a string field with the value 0 (after the bias is subtracted) as a way of encoding null bytes.

252

End of file. This code may or may not appear at the end of the data stream. PSPP always outputs this code but its use is not required.

253

A numeric or string value that is not compressible. The value is stored in the 8 bytes following the current block of command bytes. If this value appears twice in a block of command bytes, then it indicates the second group of 8 bytes following the command bytes, and so on.

254

An 8-byte string value that is all spaces.

255

The system-missing value.

The end of the 8-byte group of bytecodes is followed by any 8-byte blocks of non-compressible values indicated by code 253. After that follows another 8-byte group of bytecodes, then those bytecodes’ non-compressible values. The pattern repeats to the end of the file or a code with value 252.

2: ZLIB compression

The data record consists of the following, in order:

The ZLIB data header has the following format:

int64               zheader_ofs;
int64               ztrailer_ofs;
int64               ztrailer_len;
int64 zheader_ofs;

The offset, in bytes, of the beginning of this structure within the system file.

int64 ztrailer_ofs;

The offset, in bytes, of the first byte of the ZLIB data trailer.

int64 ztrailer_len;

The number of bytes in the ZLIB data trailer. This and the previous field sum to the size of the system file in bytes.

The data header is followed by (ztrailer_ofs - 24) / 24 ZLIB compressed data blocks. Each ZLIB compressed data block begins with a ZLIB header as specified in RFC 1950, e.g. hex bytes 78 01 (the only header yet observed in practice). Each block decompresses to a fixed number of bytes (in practice only 0x3ff000-byte blocks have been observed), except that the last block of data may be shorter. The last ZLIB compressed data block gends just before offset ztrailer_ofs.

The result of ZLIB decompression is bytecode compressed data as described above for compression format 1.

The ZLIB data trailer begins with the following 24-byte fixed header:

int64               bias;
int64               zero;
int32               block_size;
int32               n_blocks;
int64 int_bias;

The compression bias as a negative integer, e.g. if bias in the file header record is 100.0, then int_bias is -100 (this is the only value yet observed in practice).

int64 zero;

Always observed to be zero.

int32 block_size;

The number of bytes in each ZLIB compressed data block, except possibly the last, following decompression. Only 0x3ff000 has been observed so far.

int32 n_blocks;

The number of ZLIB compressed data blocks, always exactly (ztrailer_ofs - 24) / 24.

The fixed header is followed by n_blocks 24-byte ZLIB data block descriptors, each of which describes the compressed data block corresponding to its offset. Each block descriptor has the following format:

int64               uncompressed_ofs;
int64               compressed_ofs;
int32               uncompressed_size;
int32               compressed_size;
int64 uncompressed_ofs;

The offset, in bytes, that this block of data would have in a similar system file that uses compression format 1. This is zheader_ofs in the first block descriptor, and in each succeeding block descriptor it is the sum of the previous desciptor’s uncompressed_ofs and uncompressed_size.

int64 compressed_ofs;

The offset, in bytes, of the actual beginning of this compressed data block. This is zheader_ofs + 24 in the first block descriptor, and in each succeeding block descriptor it is the sum of the previous descriptor’s compressed_ofs and compressed_size. The final block descriptor’s compressed_ofs and compressed_size sum to ztrailer_ofs.

int32 uncompressed_size;

The number of bytes in this data block, after decompression. This is block_size in every data block except the last, which may be smaller.

int32 compressed_size;

The number of bytes in this data block, as stored compressed in this system file.


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Appendix C SPSS/PC+ System File Format

SPSS/PC+, first released in 1984, was a simplified version of SPSS for IBM PC and compatible computers. It used a data file format related to the one described in the previous chapter, but simplified and incompatible. The SPSS/PC+ software became obsolete in the 1990s, so files in this format are rarely encountered today. Nevertheless, for completeness, and because it is not very difficult, it seems worthwhile to support at least reading these files. This chapter documents this format, based on examination of a corpus of about 60 files from a variety of sources.

System files use four data types: 8-bit characters, 16-bit unsigned integers, 32-bit unsigned integers, and 64-bit floating points, called here char, uint16, uint32, and flt64, respectively. Data is not necessarily aligned on a word or double-word boundary.

SPSS/PC+ ran only on IBM PC and compatible computers. Therefore, values in these files are always in little-endian byte order. Floating-point numbers are always in IEEE 754 format.

SPSS/PC+ system files represent the system-missing value as -1.66e308, or f5 1e 26 02 8a 8c ed ff expressed as hexadecimal. (This is an unusual choice: it is close to, but not equal to, the largest negative 64-bit IEEE 754, which is about -1.8e308.)

Text in SPSS/PC+ system file is encoded in ASCII-based 8-bit MS DOS codepages. The corpus used for investigating the format were all ASCII-only.

An SPSS/PC+ system file begins with the following 256-byte directory:

uint32              two;
uint32              zero;
struct {
    uint32          ofs;
    uint32          len;
} records[15];
char                filename[128];
uint32 two;
uint32 zero;

Always set to 2 and 0, respectively.

These fields could be used as a signature for the file format, but the product field in record 0 seems more likely to be unique (see Record 0 Main Header Record).

struct { … } records[15];

Each of the elements in this array identifies a record in the system file. The ofs is a byte offset, from the beginning of the file, that identifies the start of the record. len specifies the length of the record, in bytes. Many records are optional or not used. If a record is not present, ofs and len for that record are both are zero.

char filename[128];

In most files in the corpus, this field is entirely filled with spaces. In one file, it contains a file name, followed by a null bytes, followed by spaces to fill the remainder of the field. The meaning is unknown.

The following sections describe the contents of each record, identified by the index into the records array.


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C.1 Record 0: Main Header Record

All files in the corpus have this record at offset 0x100 with length 0xb0 (but readers should find this record, like the others, via the records table in the directory). Its format is:

uint16              one0;
char                product[62];
flt64               sysmis;
uint32              zero0;
uint32              zero1;
uint16              one1;
uint16              compressed;
uint16              nominal_case_size;
uint16              n_cases0;
uint16              weight_index;
uint16              zero2;
uint16              n_cases1;
uint16              zero3;
char                creation_date[8];
char                creation_time[8];
char                label[64];
uint16 one0;
uint16 one1;

Always set to 1.

uint32 zero0;
uint32 zero1;
uint16 zero2;
uint16 zero3;

Always set to 0.

It seems likely that one of these variables is set to 1 if weighting is enabled, but none of the files in the corpus is weighted.

char product[62];

Name of the program that created the file. Only the following unique values have been observed, in each case padded on the right with spaces:

DESPSS/PC+ System File Written by Data Entry II
PCSPSS SYSTEM FILE.  IBM PC DOS, SPSS/PC+
PCSPSS SYSTEM FILE.  IBM PC DOS, SPSS/PC+ V3.0
PCSPSS SYSTEM FILE.  IBM PC DOS, SPSS for Windows

Thus, it is reasonable to use the presence of the string ‘SPSS’ at offset 0x104 as a simple test for an SPSS/PC+ data file.

flt64 sysmis;

The system-missing value, as described previously (see SPSS/PC+ System File Format).

uint16 compressed;

Set to 0 if the data in the file is not compressed, 1 if the data is compressed with simple bytecode compression.

uint16 nominal_case_size;

Number of data elements per case. This is the number of variables, except that long string variables add extra data elements (one for every 8 bytes after the first 8). String variables in SPSS/PC+ system files are limited to 255 bytes.

uint16 n_cases0;
uint16 n_cases1;

The number of cases in the data record. Both values are the same. Some files in the corpus contain data for the number of cases noted here, followed by garbage that somewhat resembles data.

uint16 weight_index;

0, if the file is unweighted, otherwise a 1-based index into the data record of the weighting variable, e.g. 4 for the first variable after the 3 system-defined variables.

char creation_date[8];

The date that the file was created, in ‘mm/dd/yy’ format. Single-digit days and months are not prefixed by zeros. The string is padded with spaces on right or left or both, e.g. ‘_2/4/93_’, ‘10/5/87_’, and ‘_1/11/88’ (with ‘_’ standing in for a space) are all actual examples from the corpus.

char creation_time[8];

The time that the file was created, in ‘HH:MM:SS’ format. Single-digit hours are padded on a left with a space. Minutes and seconds are always written as two digits.

char file_label[64];

File label declared by the user, if any (see FILE LABEL in PSPP Users Guide). Padded on the right with spaces.


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C.2 Record 1: Variables Record

The variables record most commonly starts at offset 0x1b0, but it can be placed elsewhere. The record contains instances of the following 32-byte structure:

uint32              value_label_start;
uint32              value_label_end;
uint32              var_label_ofs;
uint32              format;
char                name[8];
union {
    flt64           f;
    char            s[8];
} missing;

The number of instances is the nominal_case_size specified in the main header record. There is one instance for each numeric variable and each string variable with width 8 bytes or less. String variables wider than 8 bytes have one instance for each 8 bytes, rounding up. The first instance for a long string specifies the variable’s correct dictionary information. Subsequent instances for a long string are generally filled with all-zero bytes, although the missing field contains the numeric system-missing value, and some writers also fill in var_label_ofs, format, and name, sometimes filling the latter with the numeric system-missing value rather than a text string. Regardless of the values used, readers should ignore the contents of these additional instances for long strings.

uint32 value_label_start;
uint32 value_label_end;

For a variable with value labels, these specify offsets into the label record of the start and end of this variable’s value labels, respectively. See Record 2 Labels Record, for more information.

For a variable without any value labels, these are both zero.

A long string variable may not have value labels.

uint32 var_label_ofs;

For a variable with a variable label, this specifies an offset into the label record. See Record 2 Labels Record, for more information.

For a variable without a variable label, this is zero.

uint32 format;

The variable’s output format, in the same format used in system files. See System File Output Formats, for details. SPSS/PC+ system files only use format types 5 (F, for numeric variables) and 1 (A, for string variables).

char name[8];

The variable’s name, padded on the right with spaces.

union { … } missing;

A user-missing value. For numeric variables, missing.f is the variable’s user-missing value. For string variables, missing.s is a string missing value. A variable without a user-missing value is indicated with missing.f set to the system-missing value, even for string variables (!). A Long string variable may not have a missing value.

In addition to the user-defined variables, every SPSS/PC+ system file contains, as its first three variables, the following system-defined variables, in the following order. The system-defined variables have no variable label, value labels, or missing values.

$CASENUM

A numeric variable with format F8.0. Most of the time this is a sequence number, starting with 1 for the first case and counting up for each subsequent case. Some files skip over values, which probably reflects cases that were deleted.

$DATE

A string variable with format A8. Same format (including varying padding) as the creation_date field in the main header record (see Record 0 Main Header Record). The actual date can differ from creation_date and from record to record. This may reflect when individual cases were added or updated.

$WEIGHT

A numeric variable with format F8.2. This represents the case’s weight; SPSS/PC+ files do not have a user-defined weighting variable. If weighting has not been enabled, every case has value 1.0.


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C.3 Record 2: Labels Record

The labels record holds value labels and variable labels. Unlike the other records, it is not meant to be read directly and sequentially. Instead, this record must be interpreted one piece at a time, by following pointers from the variables record.

The value_label_start, value_label_end, and var_label_ofs fields in a variable record are all offsets relative to the beginning of the labels record, with an additional 7-byte offset. That is, if the labels record starts at byte offset labels_ofs and a variable has a given var_label_ofs, then the variable label begins at byte offset labels_ofs + var_label_ofs + 7 in the file.

A variable label, starting at the offset indicated by var_label_ofs, consists of a one-byte length followed by the specified number of bytes of the variable label string, like this:

uint8               length;
char                s[length];

A set of value labels, extending from value_label_start to value_label_end (exclusive), consists of a numeric or string value followed by a string in the format just described. String values are padded on the right with spaces to fill the 8-byte field, like this:

union {
    flt64           f;
    char            s[8];
} value;
uint8               length;
char                s[length];

The labels record begins with a pair of uint32 values. The first of these is always 3. The second is between 8 and 16 less than the number of bytes in the record. Neither value is important for interpreting the file.


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C.4 Record 3: Data Record

The format of the data record varies depending on the value of compressed in the file header record:

0: no compression

Data is arranged as a series of 8-byte elements, one per variable instance variable in the variable record (see Record 1 Variables Record). Numeric values are given in flt64 format; string values are literal characters string, padded on the right with spaces when necessary to fill out 8-byte units.

1: bytecode compression

The first 8 bytes of the data record is divided into a series of 1-byte command codes. These codes have meanings as described below:

0

The system-missing value.

1

A numeric or string value that is not compressible. The value is stored in the 8 bytes following the current block of command bytes. If this value appears twice in a block of command bytes, then it indicates the second group of 8 bytes following the command bytes, and so on.

2 through 255

A number with value code - 100, where code is the value of the compression code. For example, code 105 indicates a numeric variable of value 5.

The end of the 8-byte group of bytecodes is followed by any 8-byte blocks of non-compressible values indicated by code 1. After that follows another 8-byte group of bytecodes, then those bytecodes’ non-compressible values. The pattern repeats up to the number of cases specified by the main header record have been seen.

The corpus does not contain any files with command codes 2 through 95, so it is possible that some of these codes are used for special purposes.

Cases of data often, but not always, fill the entire data record. Readers should stop reading after the number of cases specified in the main header record. Otherwise, readers may try to interpret garbage following the data as additional cases.


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C.5 Records 4 and 5: Data Entry

Records 4 and 5 appear to be related to SPSS/PC+ Data Entry.


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D SPSS Viewer File Format

SPSS Viewer or .spv files, here called SPV files, are written by SPSS 16 and later to represent the contents of its output editor. This chapter documents the format, based on examination of a corpus of about 500 files from a variety of sources. This description is detailed enough to read SPV files, but probably not enough to write them.

SPSS 15 and earlier versions use a completely different output format based on the Microsoft Compound Document Format. This format is not documented here.

An SPV file is a Zip archive that can be read with zipinfo and unzip and similar programs. The final member in the Zip archive is a file named META-INF/MANIFEST.MF. This structure makes SPV files resemble Java “JAR” files (and ODF files), but whereas a JAR manifest contains a sequence of colon-delimited key/value pairs, an SPV manifest contains the string ‘allowPivoting=true’, without a new-line. (This string may be the best way to identify an SPV file; it is invariant across the corpus.)

The rest of the members in an SPV file’s Zip archive fall into two categories: structure and detail members. Structure member names begin with outputViewernnnnnnnnnn, where each n is a decimal digit, and end with .xml, and often include the string _heading in between. Each of these members represents some kind of output item (a table, a heading, a block of text, etc.) or a group of them. The member whose output goes at the beginning of the document is numbered 0, the next member in the output is numbered 1, and so on.

Structure members contain XML. This XML is sometimes self-contained, but it often references detail members in the Zip archive, which are named as follows:

prefix_table.xml and prefix_tableData.bin
prefix_lightTableData.bin

The structure of a table plus its data. Older SPV files pair a prefix_table.xml file that describes the table’s structure with a binary prefix_tableData.bin file that gives its data. Newer SPV files (the majority of those in the corpus) instead include a single prefix_lightTableData.bin file that incorporates both into a single binary format.

prefix_warning.xml and prefix_warningData.bin
prefix_lightWarningData.bin

Same format used for tables, with a different name.

prefix_notes.xml and prefix_notesData.bin
prefix_lightNotesData.bin

Same format used for tables, with a different name.

prefix_chartData.bin and prefix_chart.xml

The structure of a chart plus its data. Charts do not have a “light” format.

prefix_pmml.scf
prefix_stats.scf
prefix_model.xml

Not yet investigated. The corpus contains few examples.

The prefix in the names of the detail members is typically an 11-digit decimal number that increases for each item, tending to skip values. Older SPV files use different naming conventions. Structure member refer to detail members by name, and so their exact names do not matter to readers as long as they are unique.


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D.1 Structure Member Format

Structure members’ XML files claim conformance with a collection of XML Schemas. These schemas are distributed, under a nonfree license, with SPSS binaries. Fortunately, the schemas are not necessary to understand the structure members. To a degree, the schemas can even be deceptive because they document elements and attributes that are not in the corpus and do not document elements and attributes that are commonly found there.

Structure members use a different XML namespace for each schema, but these namespaces are not entirely consistent. In some SPV files, for example, the viewer-tree schema is associated with namespace ‘http://xml.spss.com/spss/viewer-tree’ and in others with ‘http://xml.spss.com/spss/viewer/viewer-tree’ (note the additional viewer/). Under either name, the schema URIs are not resolvable to obtain the schemas themselves.

One may ignore all of the above in interpreting a structure member. The actual XML has a simple and straightforward form that does not require a reader to take schemas or namespaces into account.

The elements found in structure members are documented below. For each element, we note the possible parent elements and the element’s contents. The contents are specified as pseudo-regular expressions with the following conventions:

text

XML text content.

CDATA

XML CDATA content.

element

The named element.

(…)

Grouping multiple elements.

[x]

An optional x.

a | b

A choice between a and b.

x*

Zero or more x.

For a diagram illustrating the hierarchy of elements within an SPV structure member, please refer to a PDF version of the manual.


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D.1.1 The heading Element

Parent: Document root or heading
Contents: [pageSetup] label (container | heading)*

The root of a structure member is a heading, which represents a section of output beginning with a title (the label) and ordinarily followed by content containers or further nested (sub)-sections of output.

The document root heading, only, may also contain a pageSetup element.

The following attributes have been observed on both document root and nested heading elements.

Optional: creator-version

The version of the software that created this SPV file. A string of the form xxyyzzww represents software version xx.yy.zz.ww, e.g. 21000001 is version 21.0.0.1. Trailing pairs of zeros are sometimes omitted, so that 21, 210000, and 21000000 are all version 21.0.0.0 (and the corpus contains all three of those forms).

The following attributes have been observed on document root heading elements only:

Optional: creator

The directory in the file system of the software that created this SPV file.

Optional: creation-date-time

The date and time at which the SPV file was written, in a locale-specific format, e.g. Friday, May 16, 2014 6:47:37 PM PDT or lunedì 17 marzo 2014 3.15.48 CET or even Friday, December 5, 2014 5:00:19 o'clock PM EST.

Optional: lockReader

Whether a reader should be allowed to edit the output. The possible values are true and false, but the corpus only contains false.

Optional: schemaLocation

This is actually an XML Namespace attribute. A reader may ignore it.

The following attributes have been observed only on nested heading elements:

Required: commandName

The locale-invariant name of the command that produced the output, e.g. Frequencies, T-Test, Non Par Corr.

Optional: visibility

To what degree the output represented by the element is visible. The only observed value is collapsed.

Optional: locale

The locale used for output, in Windows format, which is similar to the format used in Unix with the underscore replaced by a hyphen, e.g. en-US, en-GB, el-GR, sr-Cryl-RS.

Optional: olang

The output language, e.g. en, it, es, de, pt-BR.


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D.1.2 The label Element

Parent: heading or container
Contents: text

Every heading and container holds a label as its first child. The root heading in a structure member always contains the string “Output”. Otherwise, the text in label describes what it labels, often by naming the statistical procedure that was executed, e.g. “Frequencies” or “T-Test”. Labels are often very generic, especially within a container, e.g. “Title” or “Warnings” or “Notes”. Label text is localized according to the output language, e.g. in Italian a frequency table procedure is labeled “Frequenze”.

The corpus contains one example of an empty label, one that contains no text.

This element has no attributes.


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D.1.3 The container Element

Parent: heading
Contents: label [table | text]

A container serves to label a table or a text item.

This element has the following attributes.

Required: visibility

Either visible or hidden, this indicates whether the container’s content is displayed.

Optional: text-align

Presumably indicates the alignment of text within the container. The only observed value is left. Observed with nested table and text elements.

Optional: width

The width of the container in the form npx, e.g. 1097px.


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D.1.4 The text Element (Inside container)

Parent: container
Contents: html

This text element is nested inside a container. There is a different text element that is nested inside a pageParagraph.

This element has the following attributes.

Required: type

One of title, log, or text.

Optional: commandName

As on the heading element. For output not specific to a command, this is simply log. The corpus contains one example of where commandName is present but set to the empty string.

Optional: creator-version

As on the heading element.


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D.1.5 The html Element

Parent: text
Contents: CDATA

The CDATA contains an HTML document. In some cases, the document starts with <html> and ends with </html; in others the html element is implied. Generally the HTML includes a head element with a CSS stylesheet. The HTML body often begins with <BR>. The actual content ranges from trivial to simple: just discarding the CSS and tags yields readable results.

This element has the following attributes.

Required: lang

This always contains en in the corpus.


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D.1.6 The table Element

Parent: container
Contents: tableStructure

This element has the following attributes.

Required: commandName

As on the heading element.

Required: type

One of table, note, or warning.

Required: subType

The locale-invariant name for the particular kind of output that this table represents in the procedure. This can be the same as commandName e.g. Frequencies, or different, e.g. Case Processing Summary. Generic subtypes Notes and Warnings are often used.

Required: tableId

A number that uniquely identifies the table within the SPV file, typically a large negative number such as -4147135649387905023.

Optional: creator-version

As on the heading element. In the corpus, this is only present for version 21 and up and always includes all 8 digits.


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D.1.7 The tableStructure Element

Parent: table
Contents: dataPath

This element has no attributes.


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D.1.8 The dataPath Element

Parent: tableStructure
Contents: text

Contains the name of the Zip member that holds the table details, e.g. 0000000001437_lightTableData.bin.

This element has no attributes.


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D.1.9 The pageSetup Element

Parent: heading
Contents: pageHeader pageFooter

This element has the following attributes.

Required: initial-page-number

Always 1.

Optional: chart-size

Always as-is or a localization (!) of it (e.g. dimensione attuale, Wie vorgegeben).

Optional: margin-left
Optional: margin-right
Optional: margin-top
Optional: margin-bottom

Margin sizes in the form sizein, e.g. 0.25in.

Optional: paper-height
Optional: paper-width

Paper sizes in the form sizein, e.g. 8.5in by 11in for letter paper or 8.267in by 11.692in for A4 paper.

Optional: reference-orientation

Always 0deg.

Optional: space-after

Always 12pt.


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D.1.10 The pageHeader and pageFooter Elements

Parent: pageSetup
Contents: pageParagraph*

This element has no attributes.


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D.1.11 The pageParagraph Element

Parent: pageHeader or pageFooter
Contents: text

Text to go at the top or bottom of a page, respectively.

This element has no attributes.


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D.1.12 The text Element (Inside pageParagraph)

Parent: pageParagraph
Contents: [CDATA]

This text element is nested inside a pageParagraph. There is a different text element that is nested inside a container.

The element is either empty, or contains CDATA that holds almost-XHTML text: in the corpus, either an html or p element. It is almost-XHTML because the html element designates the default namespace as http://xml.spss.com/spss/viewer/viewer-tree instead of an XHTML namespace, and because the CDATA can contain substitution variables: &[Page] for the page number and &[PageTitle] for the page title.

Typical contents (indented for clarity):

<html xmlns="http://xml.spss.com/spss/viewer/viewer-tree">
    <head></head>
    <body>
        <p style="text-align:right; margin-top: 0">Page &[Page]</p>
    </body>
</html>

This element has the following attributes.

Required: type

Always text.


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D.2 Light Detail Member Format

This section describes the format of “light” detail .bin members. These members have a binary format which we describe here in terms of a context-free grammar using the following conventions:

NonTerminal ⇒ …

Nonterminals have CamelCaps names, and ⇒ indicates a production. The right-hand side of a production is often broken across multiple lines. Break points are chosen for aesthetics only and have no semantic significance.

00, 01, …, ff.

Bytes with fixed values are written in hexadecimal:

i0, i1, …, i9, i10, i11, …

32-bit integers with fixed values are written in decimal, prefixed by ‘i’.

byte

An arbitrary byte.

int

An arbitrary 32-bit integer.

double

An arbitrary 64-bit IEEE floating-point number.

string

A 32-bit integer followed by the specified number of bytes of character data. (The encoding is indicated by the Formats nonterminal.)

x?

x is optional, e.g. 00? is an optional zero byte.

x*n

x is repeated n times, e.g. byte*10 for ten arbitrary bytes.

x[name]

Gives x the specified name. Names are used in textual explanations. They are also used, also bracketed, to indicate counts, e.g. int[n] byte*[n] for a 32-bit integer followed by the specified number of arbitrary bytes.

a | b

Either a or b.

(x)

Parentheses are used for grouping to make precedence clear, especially in the presence of |, e.g. in 00 (01 | 02 | 03) 00.

count(x)

A 32-bit integer that indicates the number of bytes in x, followed by x itself.

v1(x)

In a version 1 .bin member, x; in version 3, nothing. (The .bin header indicates the version.)

v3(x)

In a version 3 .bin member, x; in version 1, nothing.

All integer and floating-point values in this format use little-endian byte order.

A “light” detail member .bin consists of a number of sections concatenated together, terminated by a byte 01:

LightMember ⇒ Header Title Caption Footnotes Fonts Formats Dimensions Data 01

The following sections go into more detail.


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D.2.1 Header

An SPV file begins with an 39-byte header:

Header ⇒
    01 00
    (i1 | i3)[version]
    01 (00 | 01) byte*21 00 00
    int[table-id] byte*4

version is a version number that affects the interpretation of some of the other data in the member. We will refer to “version 1” and “version 3” later on and use v1(…) and v3(…) for version-specific formatting (as described previously).

table-id is a binary version of the tableId attribute in the structure member that refers to the detail member. For example, if tableId is -4154297861994971133, then table-id would be 0xdca00003.

The meaning of the other variable parts of the header is not known.


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D.2.2 Title

Title ⇒
    Value[title1] 01?
    Value[c] 01? 31
    Value[title2] 01? 00? 58

The Title, which follows the Header, specifies the pivot table’s title twice, as title1 and title2. In the corpus, they are always the same.

Whereas the Value in title1 and in title2 are appropriate for presentation, and localized to the user’s language, c is in English, sometimes less specific, and sometimes less well formatted. For example, for a frequency table, title1 and title2 name the variable and c is simply “Frequencies”.


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D.2.3 Caption

Caption ⇒ 58 | 31 Value[caption]

The caption, if presented, is shown below the table.


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D.2.4 Footnotes

Footnotes ⇒ int[n] Footnote*[n]
Footnote ⇒ Value[text] (58 | 31 Value[marker]) byte*4

Each footnote has text and an optional customer marker (such as ‘*’).


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D.2.5 Fonts

Fonts ⇒ 00 Font*8
Font ⇒
    byte[index] 31 string[typeface] 00 00
    (10 | 20 | 40 | 50 | 70 | 80)[f1] 41
    (i0 | i1 | i2)[f2] 00
    (i0 | i2 | i64173)[f3]
    (i0 | i1 | i2 | i3)[f4]
    string[fgcolor] string[bgcolor] i0 i0 00
    v3(int[f5] int[f6] int[f7] int[f8]))

Each Font represents the font style for a different element, in the following order: title, caption, footnote, row labels, column labels, corner labels, data, and layers.

index is the 1-based index of the Font, i.e. 1 for the first Font, through 8 for the final Font.

typeface is the string name of the font. In the corpus, this is SansSerif in over 99% of instances and Times New Roman in the rest.

fgcolor and bgcolor are the foreground color and background color, respectively. In the corpus, these are always #000000 and #ffffff, respectively.

The meaning of the remaining data is unknown. It seems likely to include font sizes, horizontal and vertical alignment, attributes such as bold or italic, and margins.

The table below lists the values observed in the corpus. When a cell contains a single value, then 99+% of the corpus contains that value. When a cell contains a pair of values, then the first value is seen in about two-thirds of the corpus and the second value in about the remaining one-third. In fonts that include multiple pairs, values are correlated, that is, for font 3, f5 = 24, f6 = 24, f7 = 2 appears about two-thirds of the time, as does the combination of f4 = 0, f6 = 10 for font 7.

fontf1f2f3f4f5f6f7f8
140100810/1118
240021810/1111
34002124/1124/ 82/34
440023810/1111
540001810/1114
640021810/1114
7400641730/1810/1111
840023810/1114

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D.2.6 Formats

Formats ⇒
    int[n1] byte*[n1]
    int[n2] byte*[n2]
    int[n3] byte*[n3]
    int[n4] int*[n4]
    string[encoding]
    (i0 | i-1) (00 | 01) 00 (00 | 01)
    int
    byte[decimal] byte[grouping]
    int[n-ccs] string*[n-ccs]
    v1(i0)
    v3(count(count(X5) count(X6)))

X5 ⇒ byte*33 int[n] int*[n]
X6 ⇒
    01 00 (03 | 04) 00 00 00
    string[command] string[subcommand]
    string[language] string[charset] string[locale]
    (00 | 01) 00 (00 | 01) (00 | 01)
    int
    byte[decimal] byte[grouping]
    byte*8 01
    (string[dataset] string[datafile] i0 int i0)?
    int[n-ccs] string*[n-ccs]
    2e (00 | 01) (i2000000 i0)?

In every example in the corpus, n1 is 240. The meaning of the bytes that follow it is unknown.

In every example in the corpus, n2 is 18 and the bytes that follow it are 00 00 00 01 00 00 00 00 00 00 00 00 00 02 00 00 00 00. The meaning of these bytes is unknown.

In every example in the corpus for version 1, n3 is 16 and the bytes that follow it are 00 00 00 01 00 00 00 01 00 00 00 00 01 01 01 01. In version 3, observed n3 varies from 117 to 150, and its bytes include a 1-byte count at offset 0x34. When the count is nonzero, a text string of that length at offset 0x35 is the name of a “TableLook”, e.g. “Default” or “Academic”.

Observed values of n4 vary from 0 to 17. Out of 7,060 examples in the corpus, it is nonzero only 36 times.

encoding is a character encoding, usually a Windows code page such as en_US.windows-1252 or it_IT.windows-1252. The rest of the character strings in the member use this encoding. The encoding string is itself encoded in US-ASCII.

decimal is the decimal point character. The observed values are ‘.’ and ‘,’.

grouping is the grouping character. Usually, it is ‘,’ if decimal is ‘.’, and vice versa. Other observed values are ‘'’ (apostrophe), ‘ ’ (space), and zero (presumably indicating that digits should not be grouped).

n-ccs is observed as either 0 or 5. When it is 5, the following strings are CCA through CCE format strings. See Custom Currency Formats in PSPP. Most commonly these are all -,,, but other strings occur.


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D.2.7 Dimensions

A pivot table presents multidimensional data. A Dimension identifies the categories associated with each dimension.

Dimensions ⇒ int[n-dims] Dimension*[n-dims]
Dimension ⇒ Value[name] DimUnknown int[n-categories] Category*[n-categories]
DimUnknown ⇒
    byte[d1]
    (00 | 01 | 02)[d2]
    (i0 | i2)[d3]
    (00 | 01)[d4]
    (00 | 01)[d5]
    01
    int[d6]

name is the name of the dimension, e.g. Variables, Statistics, or a variable name.

d1 is usually 0 but many other values have been observed.

d3 is 2 over 99% of the time.

d5 is 0 over 99% of the time.

d6 is either -1 or the 0-based index of the dimension, e.g. 0 for the first dimension, 1 for the second, and so on. The latter is the case 98% of the time in the corpus.


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D.2.8 Categories

Categories are arranged in a tree. Only the leaf nodes in the tree are really categories; the others just serve as grouping constructs.

Category ⇒ Value[name] (Leaf | Group)
Leaf ⇒ 00 00 00 i2 int[index] i0
Group ⇒
    (00 | 01)[merge] 00 01 (i0 | i2)[data]
    i-1 int[n-subcategories] Category*[n-subcategories]

name is the name of the category (or group).

A Leaf represents a leaf category. The Leaf’s index is a nonnegative integer less than n-categories in the Dimension in which the Category is nested (directly or indirectly).

A Group represents a Group of nested categories. Usually a Group contains at least one Category, so that n-subcategories is positive, but a few Groups with n-subcategories 0 has been observed.

If a Group’s merge is 00, the most common value, then the group is really a distinct group that should be represented as such in the visual representation and user interface. If merge is 01, the categories in this group should be shown and treated as if they were direct children of the group’s containing group (or if it has no parent group, then direct children of the dimension), and this group’s name is irrelevant and should not be displayed. (Merged groups can be nested!)

A Group’s data appears to be i2 when all of the categories within a group are leaf categories that directly represent data values for a variable (e.g. in a frequency table or crosstabulation, a group of values in a variable being tabulated) and i0 otherwise.


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D.2.9 Data

The final part of an SPV light member contains the actual data.

Data ⇒
    int[layers] int[rows] int[columns] int*[n-dimensions]
    int[n-data] Datum*[n-data]
Datum ⇒ int64[index] v3(00?) Value

The values of layers, rows, and columns each specifies the number of dimensions displayed in layers, rows, and columns, respectively. Any of them may be zero. Their values sum to n-dimensions from Dimensions (see SPV Light Member Dimensions).

The n-dimensions integers are a permutation of the 0-based dimension numbers. The first layers integers specify each of the dimensions represented by layers, the next rows integers specify the dimensions represented by rows, and the final columns integers specify the dimensions represented by columns. When there is more than one dimension of a given kind, the inner dimensions are given first.

The format of a Datum varies slightly from version 1 to version 3: in version 1 it allows for an extra optional 00 byte.

A Datum consists of an index and a Value. Suppose there are d dimensions and dimension i, 0 \le i < d, has n_i categories. Consider the datum at coordinates x_i, 0 \le i < d, and note that 0 \le x_i < n_i. Then the index is calculated by the following algorithm:

let index = 0
for each i from 0 to d - 1:
    index = (n_i \times index) + x_i

For example, suppose there are 3 dimensions with 3, 4, and 5 categories, respectively. The datum at coordinates (1, 2, 3) has index 5 \times (4 \times (3 \times 0 + 1) + 2) + 3 = 33.


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D.2.10 Value

Value is used throughout the SPV light member format. It boils down to a number or a string.

Value ⇒ 00? 00? 00? 00? RawValue
RawValue ⇒
    01 ValueMod int[format] double[x]
  | 02 ValueMod int[format] double[x]
    string[varname] string[vallab] (01 | 02 | 03)
  | 03 string[local] ValueMod string[id] string[c] (00 | 01)[type]
  | 04 ValueMod int[format] string[vallab] string[varname]
    (01 | 02 | 03) string[s]
  | 05 ValueMod string[varname] string[varlabel] (01 | 02 | 03)
  | ValueMod string[format] int[n-args] Argument*[n-args]
Argument ⇒
    i0 Value
  | int[x] i0 Value*[x+1]      /* x > 0 */

There are several possible encodings, which one can distinguish by the first nonzero byte in the encoding.

01

The numeric value x, intended to be presented to the user formatted according to format, which is in the format described for system files. See System File Output Formats, for details. Most commonly, format has width 40 (the maximum).

An x with the maximum negative double value -DBL_MAX represents the system-missing value SYSMIS. (HIGHEST and LOWEST have not been observed.) See System File Format, for more about these special values.

02

Similar to 01, with the additional information that x is a value of variable varname and has value label vallab. Both varname and vallab can be the empty string, the latter very commonly.

The meaning of the final byte is unknown. Possibly it is connected to whether the value or the label should be displayed.

03

A text string, in two forms: c is in English, and sometimes abbreviated or obscure, and local is localized to the user’s locale. In an English-language locale, the two strings are often the same, and in the cases where they differ, local is more appropriate for a user interface, e.g. c of “Not a PxP table for MCN...” versus local of “Computed only for a PxP table, where P must be greater than 1.”

c and local are always either both empty or both nonempty.

id is a brief identifying string whose form seems to resemble a programming language identifier, e.g. cumulative_percent or factor_14. It is not unique.

type is 00 for text taken from user input, such as syntax fragment, expressions, file names, data set names, and 01 for fixed text strings such as names of procedures or statistics. In the former case, id is always the empty string; in the latter case, id is still sometimes empty.

04

The string value s, intended to be presented to the user formatted according to format. The format for a string is not too interesting, and the corpus contains many clearly invalid formats like A16.39 or A255.127 or A134.1, so readers should probably ignore the format entirely.

s is a value of variable varname and has value label vallab. varname is never empty but vallab is commonly empty.

The meaning of the final byte is unknown.

05

Variable varname, which is rarely observed as empty in the corpus, with variable label varlabel, which is often empty.

The meaning of the final byte is unknown.

31 or 58

(These bytes begin a ValueMod.) A format string, analogous to printf, followed by one or more Arguments, each of which has one or more values. The format string uses the following syntax:

\%
\:
\[
\]

Each of these expands to the character following ‘\\’, to escape characters that have special meaning in format strings. These are effective inside and outside the […] syntax forms described below.

\n

Expands to a new-line, inside or outside the […] forms described below.

^i

Expands to a formatted version of argument i, which must have only a single value. For example, ^1 expands to the first argument’s value.

[:a:]i

Expands a for each of the values in i. a should contain one or more ^j conversions, which are drawn from the values for argument i in order. Some examples from the corpus:

[:^1:]1

All of the values for the first argument, concatenated.

[:^1\n:]1

Expands to the values for the first argument, each followed by a new-line.

[:^1 = ^2:]2

Expands to x = y where x is the second argument’s first value and y is its second value. (This would be used only if the argument has two values. If there were more values, the second and third values would be directly concatenated, which would look funny.)

[a:b:]i

This extends the previous form so that the first values are expanded using a and later values are expanded using b. For an unknown reason, within a the ^j conversions are instead written as %j. Some examples from the corpus:

[%1:*^1:]1

Expands to all of the values for the first argument, separated by ‘*’.

[%1 = %2:, ^1 = ^2:]1

Given appropriate values for the first argument, expands to X = 1, Y = 2, Z = 3.

[%1:, ^1:]1

Given appropriate values, expands to 1, 2, 3.

The format string is localized to the user’s locale.


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D.2.11 ValueMod

A ValueMod can specify special modifications to a Value.

ValueMod ⇒
    31 i0 (i0 | i1 string[subscript])
    v1(00 (i1 | i2) 00 00 int 00 00)
    v3(count(FormatString Style ValueModUnknown))
  | 31 i1 int[footnote-number] Format
  | 31 i2 (00 | 01 | 02) 00 (i1 | i2 | i3) Format
  | 31 i3 00 00 01 00 i2 Format
  | 58
Style ⇒ 58 | 31 01? 00? 00? 00? 01 string[fgcolor] string[bgcolor] string[typeface] byte
Format ⇒ 00 00 count(FormatString Style 58)
FormatString ⇒ count((i0 (58 | 31 string))?)
ValueModUnknown ⇒ 58 | 31 i0 i0 i0 i0 01 00 (01 | 02 | 08) 00 08 00 0a 00)

The footnote-number, if present, specifies a footnote that the Value references. The footnote’s marker is shown appended to the main text of the Value, as a superscript.

The subscript, if present, specifies a string to append to the main text of the Value, as a subscript. The subscript text is a brief indicator, e.g. ‘a’ or ‘a,b’, with its meaning indicated by the table caption. In this usage, subscripts are similar to footnotes; one apparent difference is that a Value can only reference one footnote but a subscript can list more than one letter.

The Format, if present, is a format string for substitutions using the syntax explained previously. It appears to be an English-language version of the localized format string in the Value in which the Format is nested.

The Style, if present, changes the style for this individual Value.


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D.3 Legacy Detail Member Binary Format

Whereas the light binary format represents everything about a given pivot table, the legacy binary format conceptually consists of a number of named sources, each of which consists of a number of named series, each of which is a 1-dimensional array of numbers or strings or a mix. Thus, the legacy binary member format is quite simple.

This section uses the same context-free grammar notation as in the previous section, with the following additions:

vAF(x)

In a version 0xaf legacy member, x; in other versions, nothing. (The legacy member header indicates the version; see below.)

vB0(x)

In a version 0xb0 legacy member, x; in other versions, nothing.

A legacy detail member .bin has the following overall format:

LegacyBinary ⇒
    00 byte[version] int16[n-sources] int[member-size]
    Metadata*[n-sources] Data*[n-sources]

version is a version number that affects the interpretation of some of the other data in the member. Versions 0xaf and 0xb0 are known. We will refer to “version 0xaf” and “version 0xb0” members later on.

A legacy member consists of n-sources data sources, each of which has Metadata and Data.

member-size is the size of the legacy binary member, in bytes.

The following sections go into more detail.


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D.3.1 Metadata

Metadata ⇒
    int[per-series] int[n-series] int[offset]
    vAF(byte*32[source-name])
    vB0(byte*64[source-name] int[x])

A data source consists of n-series series of data, with per-series data values per series.

source-name is a 32- or 64-byte string padded on the right with zero bytes. The names that appear in the corpus are very generic, usually tableData or source0.

A given Metadata’s offset is the offset, in bytes, from the beginning of the member to the start of the corresponding Data. This allows programs to skip to the beginning of the data for a particular source; it is also important to determine whether a source includes any string data (see SPV Legacy Member Data).

The meaning of x in version 0xb0 is unknown.


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D.3.2 Data

Data ⇒ NumericData StringData?
NumericData ⇒ NumericSeries*[n-series]
NumericSeries ⇒ byte*288[series-name] double*[per-series]

Data follow the Metadata in the legacy binary format, with sources in the same order. Each NumericSeries begins with a series-name that generally indicates its role in the pivot table, e.g. “cell”, “cellFormat”, “dimension0categories”, “dimension0group0”, followed by the numeric data, one double per element in the series. A double with the maximum negative double -DBL_MAX represents the system-missing value SYSMIS.

StringData ⇒ i1 string[source-name] Pairs Labels

Pairs ⇒ int[n-string-series] PairSeries*[n-string-series]
PairSeries ⇒ string[pair-series-name] int[n-pairs] Pair*[n-pairs]
Pair ⇒ int[i] int[j]

Labels ⇒ int[n-labels] Label*[n-labels]
Label ⇒ int[frequency] int[s]

A source may include a mix of numeric and string data values. When a source includes any string data, the data values that are strings are set to SYSMIS in the NumericSeries, and StringData follows the NumericData. A source that contains no string data omits the StringData. To reliably determine whether a source includes StringData, the reader should check whether the offset following the NumericData is the offset of the next series, as indicated by its Metadata (or the end of the member, in the case of the last source).

StringData repeats the name of the source (from Metadata).

The string data overlays the numeric data. n-string-series is the number of series within the source that include string data. More precisely, it is the 1-based index of the last series in the source that includes any string data; thus, it would be 4 if there are 5 series and only the fourth one includes string data.

Each PairSeries consists a sequence of 0 or more Pair nonterminals, each of which maps from a 0-based index within series i to a 0-based label index j, e.g. pair i = 2, j = 3, means that the third data value (with value SYSMIS) is to be replaced by the string of the fourth Label.

The labels themselves follow the pairs. The valuable part of each label is the string s. Each label also includes a frequency that reports the number of pairs that reference it (although this is not useful).


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D.4 Legacy Detail Member XML Format

This format is still under investigation.


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E Encrypted File Wrappers

SPSS 21 and later can package multiple kinds of files inside an encrypted wrapper. The wrapper has a common format, regardless of the kind of the file that it contains.

Warning: The SPSS encryption wrapper is poorly designed. It is much cheaper and faster to decrypt a file encrypted this way than if a well designed alternative were used. If you must use this format, use a 10-byte randomly generated password.


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E.1 Common Wrapper Format

This section describes the general format of an SPSS encrypted file wrapper. The following sections describe the details for each kind of encapsulated file.

An encrypted file wrapper begins with the following 36-byte header, where xxx identifies the type of file encapsulated, as described in the following sections:

0000  1c 00 00 00 00 00 00 00  45 4e 43 52 59 50 54 45  |........ENCRYPTE|
0010  44 xx xx xx 15 00 00 00  00 00 00 00 00 00 00 00  |Dxxx............|
0020  00 00 00 00                                       |....|

Following the fixed header is essentially the regular contents of the encapsulated file in its usual format, with each 16-byte block encrypted with AES-256 in ECB mode. Each type of encapsulated file is processed in a slightly different way before encryption, as described in the following sections. The AES-256 key is derived from a password in the following way:

  1. Start from the literal password typed by the user. Truncate it to at most 10 bytes, then append as many null bytes as necessary until there are exactly 32 bytes. Call this password.
  2. Let constant be the following 73-byte constant:
    0000  00 00 00 01 35 27 13 cc  53 a7 78 89 87 53 22 11
    0010  d6 5b 31 58 dc fe 2e 7e  94 da 2f 00 cc 15 71 80
    0020  0a 6c 63 53 00 38 c3 38  ac 22 f3 63 62 0e ce 85
    0030  3f b8 07 4c 4e 2b 77 c7  21 f5 1a 80 1d 67 fb e1
    0040  e1 83 07 d8 0d 00 00 01  00
    
  3. Compute CMAC-AES-256(password, constant). Call the 16-byte result cmac.
  4. The 32-byte AES-256 key is cmac || cmac, that is, cmac repeated twice.

Example

Consider the password ‘pspp’. password is:

0000  70 73 70 70 00 00 00 00  00 00 00 00 00 00 00 00  |pspp............|
0010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

cmac is:

0000  3e da 09 8e 66 04 d4 fd  f9 63 0c 2c a8 6f b0 45

The AES-256 key is:

0000  3e da 09 8e 66 04 d4 fd  f9 63 0c 2c a8 6f b0 45
0010  3e da 09 8e 66 04 d4 fd  f9 63 0c 2c a8 6f b0 45

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E.1.1 Encrypted System Files

An encrypted system file uses SAV as the identifier in its header.

Before encryption, a system file is appended with as many null bytes as needed (possibly zero) to make it a multiple of 16 bytes in length, so that it fits exactly in a series of AES blocks. (This implies that encrypted system files must always be compressed, because otherwise a system file with only a single variable might appear to have an extra case.)


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E.1.2 Encrypted Syntax Files

An encrypted syntax file uses SPS as the identifier in its header.

Before encryption, a syntax file is prefixed with a line at the beginning of the form * Encoding: encoding., where encoding is the encoding used for the rest of the file, e.g. windows-1252. The syntax file is then appended with as many bytes with value 04 as needed (possibly zero) to make it a multiple of 16 bytes in length.


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E.2 Password Encoding

SPSS also supports what it calls “encrypted passwords.” These are not encrypted. They are encoded with a simple, fixed scheme. An encoded password is always a multiple of 2 characters long, and never longer than 20 characters. The characters in an encoded password are always in the graphic ASCII range 33 through 126. Each successive pair of characters in the password encodes a single byte in the plaintext password.

Use the following algorithm to decode a pair of characters:

  1. Let a be the ASCII code of the first character, and b be the ASCII code of the second character.
  2. Let ah be the most significant 4 bits of a. Find the line in the table below that has ah on the left side. The right side of the line is a set of possible values for the most significant 4 bits of the decoded byte.
    2 2367
    3 0145
    4789cd
    56abef
    
  3. Let bh be the most significant 4 bits of b. Find the line in the second table below that has bh on the left side. The right side of the line is a set of possible values for the most significant 4 bits of the decoded byte. Together with the results of the previous step, only a single possibility is left.
    2 139b
    3 028a
    4746ce
    5657df
    
  4. Let al be the least significant 4 bits of a. Find the line in the table below that has al on the left side. The right side of the line is a set of possible values for the least significant 4 bits of the decoded byte.
    03cf0145
    12de2367
    478b89cd
    569aabef
    
  5. Let bl be the least significant 4 bits of b. Find the line in the table below that has bl on the left side. The right side of the line is a set of possible values for the least significant 4 bits of the decoded byte. Together with the results of the previous step, only a single possibility is left.
    03cf028a
    12de139b
    478b46ce
    569a57df
    

Example

Consider the encoded character pair ‘-|’. a is 0x2d and b is 0x7c, so ah is 2, bh is 7, al is 0xd, and bl is 0xc. ah means that the most significant four bits of the decoded character is 2, 3, 6, or 7, and bh means that they are 4, 6, 0xc, or 0xe. The single possibility in common is 6, so the most significant four bits are 6. Similarly, al means that the least significant four bits are 2, 3, 6, or 7, and bl means they are 0, 2, 8, or 0xa, so the least significant four bits are 2. The decoded character is therefore 0x62, the letter ‘b’.


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Appendix F q2c Input Format

PSPP statistical procedures have a bizarre and somewhat irregular syntax. Despite this, a parser generator has been written that adequately addresses many of the possibilities and tries to provide hooks for the exceptional cases. This parser generator is named q2c.


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F.1 Invoking q2c

q2c input.q output.c

q2c translates a ‘.q’ file into a ‘.c’ file. It takes exactly two command-line arguments, which are the input file name and output file name, respectively. q2c does not accept any command-line options.


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F.2 q2c Input Structure

q2c input files are divided into two sections: the grammar rules and the supporting code. The grammar rules, which make up the first part of the input, are used to define the syntax of the statistical procedure to be parsed. The supporting code, following the grammar rules, are copied largely unchanged to the output file, except for certain escapes.

The most important lines in the grammar rules are used for defining procedure syntax. These lines can be prefixed with a dollar sign (‘$’), which prevents Emacs’ CC-mode from munging them. Besides this, a bang (‘!’) at the beginning of a line causes the line, minus the bang, to be written verbatim to the output file (useful for comments). As a third special case, any line that begins with the exact characters /* *INDENT is ignored and not written to the output. This allows .q files to be processed through indent without being munged.

The syntax of the grammar rules themselves is given in the following sections.

The supporting code is passed into the output file largely unchanged. However, the following escapes are supported. Each escape must appear on a line by itself.

/* (header) */

Expands to a series of C #include directives which include the headers that are required for the parser generated by q2c.

/* (decls scope) */

Expands to C variable and data type declarations for the variables and enums input and output by the q2c parser. scope must be either local or global. local causes the declarations to be output as function locals. global causes them to be declared as static module variables; thus, global is a bit of a misnomer.

/* (parser) */

Expands to the entire parser. Must be enclosed within a C function.

/* (free) */

Expands to a set of calls to the free function for variables declared by the parser. Only needs to be invoked if subcommands of type string are used in the grammar rules.


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F.3 Grammar Rules

The grammar rules describe the format of the syntax that the parser generated by q2c will understand. The way that the grammar rules are included in q2c input file are described above.

The grammar rules are divided into tokens of the following types:

Identifier (ID)

An identifier token is a sequence of letters, digits, and underscores (‘_’). Identifiers are not case-sensitive.

String (STRING)

String tokens are initiated by a double-quote character (‘"’) and consist of all the characters between that double quote and the next double quote, which must be on the same line as the first. Within a string, a backslash can be used as a “literal escape”. The only reasons to use a literal escape are to include a double quote or a backslash within a string.

Special character

Other characters, other than white space, constitute tokens in themselves.

The syntax of the grammar rules is as follows:

grammar-rules ::= command-name opt-prefix : subcommands .
command-name ::= ID
             ::= STRING
opt-prefix ::=
           ::= ( ID )
subcommands ::= subcommand
            ::= subcommands ; subcommand

The syntax begins with an ID token that gives the name of the procedure to be parsed. For command names that contain multiple words, a STRING token may be used instead, e.g. ‘"FILE HANDLE"’. Optionally, an ID in parentheses specifies a prefix used for all file-scope identifiers declared by the emitted code.

The rest of the syntax consists of subcommands separated by semicolons (‘;’) and terminated with a full stop (‘.’).

subcommand ::= default-opt arity-opt ID sbc-defn
default-opt ::=
            ::= *
arity-opt ::=
          ::= +
          ::= ^
sbc-defn ::= opt-prefix = specifiers
         ::= [ ID ] = array-sbc
         ::= opt-prefix = sbc-special-form

A subcommand that begins with an asterisk (‘*’) is the default subcommand. The keyword used for the default subcommand can be omitted in the PSPP syntax file.

A plus sign (‘+’) indicates that a subcommand can appear more than once. A caret (‘^’) indicate that a subcommand must appear exactly once. A subcommand marked with neither character may appear once or not at all, but not more than once.

The subcommand name appears after the leading option characters.

There are three forms of subcommands. The first and most common form simply gives an equals sign (‘=’) and a list of specifiers, which can each be set to a single setting. The second form declares an array, which is a set of flags that can be individually turned on by the user. There are also several special forms that do not take a list of specifiers.

Arrays require an additional ID argument. This is used as a prefix, prepended to the variable names constructed from the specifiers. The other forms also allow an optional prefix to be specified.

array-sbc ::= alternatives
          ::= array-sbc , alternatives
alternatives ::= ID
             ::= alternatives | ID

An array subcommand is a set of Boolean values that can independently be turned on by the user, listed separated by commas (‘,’). If an value has more than one name then these names are separated by pipes (‘|’).

specifiers ::= specifier
           ::= specifiers , specifier
specifier ::= opt-id : settings
opt-id ::=
       ::= ID

Ordinary subcommands (other than arrays and special forms) require a list of specifiers. Each specifier has an optional name and a list of settings. If the name is given then a correspondingly named variable will be used to store the user’s choice of setting. If no name is given then there is no way to tell which setting the user picked; in this case the settings should probably have values attached.

settings ::= setting
         ::= settings / setting
setting ::= setting-options ID setting-value
setting-options ::=
                ::= *
                ::= !
                ::= * !

Individual settings are separated by forward slashes (‘/’). Each setting can be as little as an ID token, but options and values can optionally be included. The ‘*’ option means that, for this setting, the ID can be omitted. The ‘!’ option means that this option is the default for its specifier.

setting-value ::=
              ::= ( setting-value-2 )
              ::= setting-value-2
setting-value-2 ::= setting-value-options setting-value-type : ID
setting-value-options ::=
                      ::= *
setting-value-type ::= N
                   ::= D
                   ::= S

Settings may have values. If the value must be enclosed in parentheses, then enclose the value declaration in parentheses. Declare the setting type as ‘n’, ‘d’, or ‘s’ for integer, floating-point, or string type, respectively. The given ID is used to construct a variable name. If option ‘*’ is given, then the value is optional; otherwise it must be specified whenever the corresponding setting is specified.

sbc-special-form ::= VAR
                 ::= VARLIST varlist-options
                 ::= INTEGER opt-list
                 ::= DOUBLE opt-list
                 ::= PINT
                 ::= STRING (the literal word STRING)
                 ::= CUSTOM
varlist-options ::=
                ::= ( STRING )
opt-list ::=
         ::= LIST

The special forms are of the following types:

VAR

A single variable name.

VARLIST

A list of variables. If given, the string can be used to provide PV_* options to the call to parse_variables.

INTEGER

A single integer value.

INTEGER LIST

A list of integers separated by spaces or commas.

DOUBLE

A single floating-point value.

DOUBLE LIST

A list of floating-point values.

PINT

A single positive integer value.

STRING

A string value.

CUSTOM

A custom function is used to parse this subcommand. The function must have prototype int custom_name (void). It should return 0 on failure (when it has already issued an appropriate diagnostic), 1 on success, or 2 if it fails and the calling function should issue a syntax error on behalf of the custom handler.


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Appendix G GNU Free Documentation License

Version 1.3, 3 November 2008
Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
http://fsf.org/

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
  1. PREAMBLE

    The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

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    This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

    A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

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  6. COMBINING DOCUMENTS

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    In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”

  7. COLLECTIONS OF DOCUMENTS

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  8. AGGREGATION WITH INDEPENDENT WORKS

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ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

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If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with…Texts.” line with this:

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If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.


Footnotes

(1)

It might also be desirable for the LC_COLLATE category to be used for the purposes of sorting data.

(2)

This part of the format may not be fully understood, because only a single example of each possibility has been examined.