6.7.1 Attributes of Variables
Each variable has a number of attributes, including:
- An identifier, up to 64 bytes long. Each variable must have a different name.
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. will be 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
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.
- Missing values
- 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 Missing Observations.
- Variable label
- A string that describes the variable. See VARIABLE LABELS.
- Value label
- Optionally, these associate each possible value of the variable with a
string. See VALUE LABELS.
- Print format
- 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.
- Write format
- Similar to print format, but used by the
- Custom attributes
- 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.