[R] Survival statistics--displaying multiple plots

Petr Klasterecky klaster at karlin.mff.cuni.cz
Thu May 3 05:57:44 CEST 2007

Have a look at
?plot - the option add, add=TRUE

You will have to specify proper limits on both axes, otherwise you may 
only see parts of the graphs. Some functions in the survival library 
also allow stratified analyses in which case the plots account for 
different strata.


Gregory Pierce napsal(a):
> I should clarify. I can generate plots for each category individually but
> not for all three on the same chart.
> Greg
> -----Original Message-----
> From: Gregory Pierce [mailto:pierce.gregory at gmail.com] 
> Sent: Wednesday, May 02, 2007 10:21 PM
> To: 'r-help at stat.math.ethz.ch'
> Subject: Survival statistics--displaying multiple plots
> Hello all!
> I am once again analyzing patient survival data with chronic liver disease. 
> The severity of the liver disease is given by a number which is continuously
> variable. I have referred to this number as "meld"--model for end stage
> liver disease--which is the result of a mathematical calculation on
> underlying laboratory values. So, for example, I can generate a Kaplan-Meier
> plot of patients undergoing a TIPS procedure with the following:
>> plot(survfit(Surv(days,status==1),subset(tips,meld<10)) 
> where "tips" is my data set, "days" is the number of days alive, and meld is
> the meld score.
> What I would like to do is display the survival graphs of patients with
> meld<10, 10<meld<20, and meld>20. I am unsure about how to go about this.
> Any suggestions would be appreciated.
> Greg
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Petr Klasterecky
Dept. of Probability and Statistics
Charles University in Prague
Czech Republic

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