Enter Expression for Time Dependent Covariates

Click the Add Time Covariate or Edit Time Covariate button in the Define Time-Dependent Covariates/Expressions dialog box to access the options described here.

Element Name Description
Covariate Enter the name of the time-dependent covariate in the Covariate box.
Expression Enter the expression/formula that defines the time-dependent covariate. The syntax rules for the expressions are identical to those for spreadsheet formulas. In addition to the available arithmetic operators and functions, the expression interpreter also recognizes the symbol t_ or T_ (i.e., letter t and underscore) to denote the survival times. By using this symbol, you can define time-dependent covariates.
Note: Expressions that do not include the symbol T_ are not valid since they are not a function of time and thus do not define time-dependent covariates.
OK Save your changes to the current time-dependent covariate.
Cancel Cancel your changes to the current time-dependent covariate.
Review vars Displays the Select Variables dialog box, where you can view the variables in the current spreadsheet and select them in order to add them to the current expression.