[R] cox.zph

[Thomas Lumley]

On Wed, 25 Jan 2006, singyee ling wrote:

> Dear R-users,
>
> I am sorry if this is obvious. I am testing the proportional hazard
> assumptions using cox.zph. If i am not wrong, a g(t) function must be
> assumed. Four possibilities available in R  are "km","identity" and "rank".
> may i know what functions of time are these transformation assuming?

It should be fairly clear what "identity", "log" and "rank" are:
   g(t)=t
   g(t)=log(t)
and the rank of the observations time, respectively.

"km" uses the Kaplan-Meier estimator of survival at time t.

 	-thomas