Next: , Up: Values   [Contents][Index]

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).