[R] help drawing kaplan-meier plot starting from 0

Frank Mattes rggefrm at ucl.ac.uk
Thu Jan 16 17:00:05 CET 2003

Dear help news reader,

I'm trying to draw a Kaplan-Meier curve and would like to ask the news 
group for some help
Supposing I have study comapring two drugs, "A", and "B" and I recorde the 
time to get to the clinical endpoint (Time), in my case becommming virus free.

I have setup the following frame:
   Time  c Drug
1    5 1    A
2    7 1    B
3    2 1    A
4   10 1    B
5    6 1    A
6    8 1    B

"c" contains the coding if sucessful or not, but I think at the moment that 
is not important.
I did

fitstudy <- survfit(Surv(Time) ~ Drug, data=study) or
fitstudy <- fitstudy <- survfit(Surv(Time, c) ~ Drug, data=study)

and than


which gives me a Kaplan-Meier Curve, starting with 1. However I would like 
to the a plot
starting with "0" and than showing the increasing numbers of patients 
becomming "virus negative".

It would be great, if someone could point me in the right direction where I 
can find the answer.

Many thanks in advance

Frank Mattes, MD
Department of Virology
Royal Free and University Medical School

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