Overview (TIME PROGRAM command)

TIME PROGRAM is required to define time-dependent covariates. These are covariates whose values change during the course of the study.

Basic Specification

The basic specification is the TIME PROGRAM command followed by one or more commands that define time-dependent covariates.

Syntax Rules

  • TIME PROGRAM and the transformations that define the time-dependent covariate(s) must precede the command that analyzes the time-dependent covariate(s).
  • A time-dependent covariate is a function of the current time, which is represented by the special variable T_.
  • The active dataset must not have a variable named T_. If it does, rename the variable. Otherwise, you will trigger an error.
  • T_ cannot be specified as a covariate. Any other variable in the TIME PROGRAM can be specified on the covariate list.
  • For every time-dependent covariate, values are generated for each valid case for all uncensored times in the same stratum that occur before the observed time. If no STRATA subcommand is specified, all cases are considered to belong to one stratum.
  • If any function defined by the time program results in a missing value for a case that has no missing values for any other variable used in the procedure, this causes an error.