MISSING Subcommand (TREE command)

The MISSING subcommand controls the handling of nominal, user-missing, independent (predictor) variable values.

• Handling of ordinal and scale user-missing independent variable values varies between growing methods.
• By default, if the values of all independent variables are system- or user-missing, the case is excluded.
• Handling of nominal dependent variables is controlled by the DEPCATEGORIES subcommand.
• For the dependent variable, cases with system-missing or user-missing ordinal or scale values are always excluded.

NOMINALMISSING Keyword

The NOMINALMISSING keyword controls the treatment of user-missing values of nominal independent (predictor) variables.

MISSING. Handling of user-missing values of nominal predictor variables depends on the growing method. This is the default.

VALID. Treat user-missing values of nominal independent variables as valid values. User-missing values of nominal independent variables are treated as ordinary values in tree growing and classification.

Method-Dependent Rules

If some, but not all independent variable values are system-or user-missing:

• For CHAID and Exhaustive CHAID, system- and user-missing scale and ordinal independent variable values are included in the tree-growing process as a "floating" category that is allowed to merge with other categories in tree nodes. By default, nominal user-missing values are also handled in this fashion.
• For CRT and QUEST, cases with missing independent variable values are excluded from the tree-growing process but are classified using surrogate predictors, if surrogates are included in the method. By default, nominal user-missing values are also handled in this fashion.

Weight Variables

If the analysis uses frequency weights or an influence variable, all cases with zero, negative, system-missing, or user-missing values of either variable are excluded from the analysis.