A value known to be numeric at compile time is represented as a
double. PSPP provides three values of
special purposes, defined in data/val-type.h:
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, for a PSPP user's view of missing values.
PSPP currently defines
-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.
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 HIas a range of missing values (see MISSING VALUES).