Define Time-Dependent Covariate/Expressions
Click the Expression(s) button on the Cox Proportional Hazards Regression - Quick tab to display the Define Time-Dependent Covariates/Expressions dialog.
Element Name | Description |
---|---|
Add Time Covariate | Displays the Enter Expression for Time Dependent Covariates dialog, which is used to add a time-dependent covariate to the design. |
Edit Time Covariate | Displays the Enter Expression for Time Dependent Covariates dialog, which is used to edit a formula for an already existing time-dependent covariate. |
Remove | Removes an already existing time dependent covariate from the design. |
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 recognizes the symbol t_ or T_ (i.e., letter t and the 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.