cox.zph               package:survival               R Documentation

Test the Proportional Hazards Assumption of a Cox Regression

Description:

     Test the proportional hazards assumption for a Cox regression
     model fit ('coxph').

Usage:

     cox.zph(fit, transform="km", global=TRUE)

Arguments:

     fit: the result of fitting a Cox regression model, using the
          'coxph' function. 

transform: a character string specifying how the survival times should
          be transformed before the test is performed. Possible values
          are '"km"', '"rank"', '"identity"' or  a function of one
          argument. 

  global: should a global chi-square test be done, in addition to the
          per-variable tests. 

Value:

     an object of class '"cox.zph"', with components:

Note:

     The 'plot' method requires the 'splines' library

References:

     P. Grambsch and T. Therneau (1994), Proportional hazards tests and
     diagnostics based on weighted residuals. _Biometrika,_ *81*,
     515-26.

See Also:

     'coxph', 'Surv'.

Examples:

     data(ovarian)
     fit <- coxph( Surv(futime, fustat) ~ age + rx, ovarian)
     temp<- cox.zph(fit)
     print(temp)                  #display the results
     plot(temp)                   #plot curves

