Each variable has a number of attributes, including:
An identifier, up to 64 bytes long. Each variable must have a different name. See Tokens.
Some system variable names begin with ‘$’, but user-defined variables’ names may not begin with ‘$’.
The final character in a variable name should not be ‘.’, because
such an identifier will be misinterpreted when it is the final token
on a line:
FOO. is divided into two separate tokens,
‘FOO’ and ‘.’, indicating end-of-command. See Tokens.
The final character in a variable name should not be ‘_’, because some such identifiers are used for special purposes by PSPP procedures.
As with all PSPP identifiers, variable names are not case-sensitive. PSPP capitalizes variable names on output the same way they were capitalized at their point of definition in the input.
Numeric or string.
(string variables only) String variables with a width of 8 characters or fewer are called short string variables. Short string variables may be used in a few contexts where long string variables (those with widths greater than 8) are not allowed.
Variables in the dictionary are arranged in a specific order.
DISPLAY can be used to show this order: see DISPLAY.
Either reinitialized to 0 or spaces for each case, or left at its existing value. See LEAVE.
Optionally, up to three values, or a range of values, or a specific value plus a range, can be specified as user-missing values. There is also a system-missing value that is assigned to an observation when there is no other obvious value for that observation. Observations with missing values are automatically excluded from analyses. User-missing values are actual data values, while the system-missing value is not a value at all. See Handling missing observations.
A string that describes the variable. See VARIABLE LABELS.
Optionally, these associate each possible value of the variable with a string. See VALUE LABELS.
Display width, format, and (for numeric variables) number of decimal places. This attribute does not affect how data are stored, just how they are displayed. Example: a width of 8, with 2 decimal places. See Input and Output Formats.
Similar to print format, but used by the
One of the following:
Each value of a nominal variable represents a distinct category. The possible categories are finite and often have value labels. The order of categories is not significant. Political parties, US states, and yes/no choices are nominal. Numeric and string variables can be nominal.
Ordinal variables also represent distinct categories, but their values
are arranged according to some natural order. Likert scales, e.g.
from strongly disagree to strongly agree, are ordinal. Data grouped
into ranges, e.g. age groups or income groups, are ordinal. Both
numeric and string variables can be ordinal. String values are
ordered alphabetically, so letter grades from A to F will work as
Scale variables are ones for which differences and ratios are meaningful. These are often values which have a natural unit attached, such as age in years, income in dollars, or distance in miles. Only numeric variables are scalar.
Variables created by
COMPUTE and similar transformations,
obtained from external sources, etc., initially have an unknown
measurement level. Any procedure that reads the data will then assign
a default measurement level. PSPP can assign some defaults without
reading the data:
Otherwise, PSPP reads the data and decides based on its distribution:
Finally, if none of the above is true, PSPP assigns the variable a nominal measurement level.
User-defined associations between names and values. See VARIABLE ATTRIBUTE.
The intended role of a variable for use in dialog boxes in graphical user interfaces. See VARIABLE ROLE.