[R] Survival statistics--displaying multiple plots

Robert A LaBudde ral at lcfltd.com
Thu May 3 07:28:38 CEST 2007

The layout() function below states there are to be 3 graphs on the 
first row, side by side.

Each time you plot, R applies the graph to the next free position on 
the layout. After 3 plots with your different boolean subsets, you 
end up with 3 graphs side by side.

If this is not what you want (you asked for this in your first 
request), and instead you want 3 curves on the same, single graph, 
use plot() for the first curve(s) and then use lines() to add the 
additional curves.

Check the survfit() object to see how to pick off individual times 
and survival curves by subscripting.

At 12:09 AM 5/3/2007, Greg wrote:
>Thanks for replying Robert. Forgive me, it might be the hour or my
>limitations, but I am a little unclear on how to implement your suggestion.
>In my original example,
> >plot(survfit(Surv(days,status==1),subset(tips,meld<10))
>A plot of the fraction of patients surviving following the procedure against
>the number of days since the procedure would be generated for patients with
>meld scores of less than 10.
>Similarly, if I wanted to generate a survival curve of patients with scores
>of between 10 and 20, I can with the following:
>  >plot(survfit(Surv(days,status==1),subset(tips,meld>10 & meld <20))
>And for patients with meld>20,
> >plot(survfit(Surv(days,status==1),subset(tips,meld>20))
>But how do I display the curves in each cadre (meld<10, 10<meld<20, and
>meld>20) on the same chart?
>-----Original Message-----
>From: Robert A LaBudde [mailto:ral at lcfltd.com]
>Sent: Wednesday, May 02, 2007 11:48 PM
>To: Gregory Pierce
>Subject: Re: [R] Survival statistics--displaying multiple plots
>? layout()
>? par()
>layout(matrix(c(1,2,3),1,3,byrow=TRUE) #3 plots side-by-side
>Then use plot() three times to generate each of your graphs.
>At 11:14 PM 5/2/2007, Greg wrote:
> >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
> >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
> >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
> >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.

Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: ral at lcfltd.com
Least Cost Formulations, Ltd.            URL: http://lcfltd.com/
824 Timberlake Drive                     Tel: 757-467-0954
Virginia Beach, VA 23464-3239            Fax: 757-467-2947

"Vere scire est per causas scire"

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