Message-ID: <499AE956.4080108@uke.uni-hamburg.de>
Date: 2009-02-17T16:44:06Z
From: Eik Vettorazzi
Subject: Survival-Analysis: How to get numerical values from survfit (and not just a plot)?
In-Reply-To: <499AD9B7.8070502@dlr.de>
Hi Bernhard,
I'm wondering what you will expect to get in "dividing" two proportional
survival curves from a fitted cox model.
Anyway, you can provide a newdata object to the survfit function
containing any combination of cofactors you are interested in and then
use summary, eg:
fit <- coxph( Surv(futime,fustat)~resid.ds+rx+ecog.ps,data=ovarian)
summary(survfit( fit,newdata=data.frame(rx=1, ecog.ps=2, resid.ds=0)))
hth.
Bernhard Reinhardt schrieb:
> Hi!
>
> I came across R just a few days ago since I was looking for a toolbox
> for cox-regression.
>
> I?ve read
> "Cox Proportional-Hazards Regression for Survival Data
> Appendix to An R and S-PLUS Companion to Applied Regression" from John
> Fox.
>
> As described therein plotting survival-functions works well
> (plot(survfit(model))). But I?d like to do some manipulation with the
> survival-functions before plotting them e.g. dividing one
> survival-function by another.
>
> survfit() only returns an object of the following structure
>
> n events median 0.9LCL 0.9UCL
> 55.000 55.000 1.033 0.696 1.637
>
> Can you tell me how I can calculate a survival- or baseline-function
> out of these values and how I extract the values from the object? I?m
> sure the calculation is done by the corresponding plot-routine, but I
> couldn?t find that one either.
>
> Regards
>
> Bernhard
>
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--
Eik Vettorazzi
Institut f?r Medizinische Biometrie und Epidemiologie
Universit?tsklinikum Hamburg-Eppendorf
Martinistr. 52
20246 Hamburg
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