Variable Lists (KNN command)

The command line variable lists specify the dependent variable, any categorical predictors (also known as factors), and any scale predictors (also known as covariates).

Dependent Variable

• An optional dependent variable must be the first specification on the KNN command.
• The dependent variable may be followed by the measurement level specification, which contains, in parentheses, the MLEVEL keyword followed by an equals sign and then S for scale, O for ordinal, or N for nominal. KNN treats ordinal and nominal dependent variables equivalently as categorical.
• If a measurement level is specified, then it temporarily overrides a dependent variable's setting in the data dictionary.
• If no measurement level is specified, then KNN defaults to the dictionary setting.
• If a measurement level is not specified and no setting is recorded in the data dictionary, then a numeric variable is treated as scale and a string variable is treated as categorical.
• Dependent variables can be numeric or string.
• A string variable may be defined as ordinal or nominal only.

Predictor Variables

• The names of the factors, if any, must be preceded by the keyword BY.
• If keyword BY is specified with no factors, then a warning is issued and BY is ignored.
• The names of the covariates, if any, must be preceded by the keyword WITH.
• If keyword WITH is specified with no covariates, then a warning is issued and WITH is ignored.
• A dependent variable may not be specified within a factor or covariate list. If a dependent variable is specified within one of these lists, then an error is issued.
• All variables specified within a factor or covariate list must be unique. If duplicate variables are specified within a list, then the duplicates are ignored.
• If duplicate variables are specified across the factor and covariate lists, then an error is issued.
• Factor variables can be numeric or string.
• Covariates must be numeric.
• At least one predictor must be specified.