survival (version 2.11-4)

cox.zph: 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:

item

• table
• x
• y
• call

code

slope=0

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