# [R] Question on survival

Chris Andrews chrisaa at umich.edu
Fri Oct 12 14:15:45 CEST 2012

```lau pel wrote
> Hi,
> I'm going crazy trying to plot a quite simple graph.
> i need to plot estimated hazard rate from a cox model.
> supposing the model i like this:
> coxPhMod=coxph(Surv(TIME, EV) ~ AGE+A+B+strata(C) data=data)
> with 4 level for C.
> how can i obtain a graph with 4 estimated (better smoothed) hazard curve
> (base-line hazard + 3 proportional) to highlight the effect of C.
> thanks!!
> laudan
>
> (1) The curves won't be proportional if you stratify on C.  The curves are
> proportional for AGE, A, and B in your model.
> (2) If you want to deal with an individual stratum, you can extract them
> individually from survfit
>
> dataset <-
>   data.frame(Time = rexp(100, 1),
>              A = rnorm(100),
>              B = rnorm(100),
>              C = factor(rep(letters[1:4],25)))
> mod <- coxph(Surv(Time) ~ A + B + strata(C), data=dataset)
>
> # first stratum fit
> survfit(mod, newdata=data.frame(A=rep(0,4), B=rep(0,4),
> C=factor(letters[1:4])))
>
>
>
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> and provide commented, minimal, self-contained, reproducible code.

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