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SPSS® 12.0 Command Syntax Reference

SPSS® 12.0 Command Syntax Reference

SPSS® 12.0 Command Syntax Reference

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Basic Specification<br />

COXREG 295<br />

• The minimum specification on COXREG is a dependent variable with the STATUS<br />

subcommand.<br />

• To analyze the influence of time-constant covariates on the survival times, the minimum<br />

specification requires either the WITH keyword followed by at least one covariate (independent<br />

variable) on the VARIABLES subcommand or a METHOD subcommand with at<br />

least one independent variable.<br />

• To analyze the influence of time-dependent covariates on the survival times, the TIME<br />

PROGRAM command and transformation language are required to define the functions for<br />

the time-dependent covariate(s).<br />

Subcommand Order<br />

• The VARIABLES subcommand must be specified first; the subcommand keyword is optional.<br />

• Remaining subcommands can be named in any order.<br />

<strong>Syntax</strong> Rules<br />

• Only one dependent variable can be specified for each COXREG command.<br />

• Any number of covariates (independent variables) can be specified. The dependent<br />

variable cannot appear on the covariate list.<br />

• The covariate list is required if any of the METHOD subcommands are used without a<br />

variable list or if the METHOD subcommand is not used.<br />

• Only one status variable can be specified on the STATUS subcommand. If multiple<br />

STATUS subcommands are specified, only the last specification is in effect.<br />

• You can use the BY keyword to specify interaction between covariates.<br />

Operations<br />

• TIME PROGRAM computes the values for time-dependent covariates.<br />

• COXREG replaces covariates specified on CATEGORICAL with sets of contrast variables.<br />

In stepwise analyses, the set of contrast variables associated with one categorical variable<br />

is entered or removed from the model as a block.<br />

• Covariates are screened to detect and eliminate redundancies.<br />

• COXREG deletes all cases that have negative values for the dependent variable.<br />

Limitations<br />

• Only one dependent variable is allowed.<br />

• Maximum 100 covariates in a single interaction term.<br />

• Maximum 35 levels for a BY variable on PATTERN.

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