Message-ID: <418F7F48.1020603@student.umu.se>
Date: 2004-11-08T14:14:32Z
From: Danardono
Subject: survSplit
In-Reply-To: <Pine.A41.4.61b.0411031035330.364448@homer10.u.washington.edu>
I am just realized that survival has the facility to do survival time
splitting survSplit
after read some postings about time dependency in the list.
Is it survSplit only for the survival data input (time,status) and not
for the 'counting process' input (start,stop,status)?
I take one example modified from the survSplit help:
>data(aml)
>aml3<-survSplit(aml,cut=c(5,10,50),end="time",start="start",event="status",episode="i",id="id")
>coxph(Surv(time,status)~x,data=aml)
coef exp(coef) se(coef) z p
xNonmaintained 0.916 2.5 0.512 1.79 0.074
Likelihood ratio test=3.38 on 1 df, p=0.0658 n= 23
#the same
>coxph(Surv(time,status)~x,data=aml3)
coef exp(coef) se(coef) z p
xNonmaintained 0.916 2.5 0.512 1.79 0.074
Likelihood ratio test=3.38 on 1 df, p=0.0658 n= 63
BUT If I split aml3 further:
>aml4<-survSplit(aml3,cut=c(9,12,40),end="time",start="start",event="status",episode="i",id="id2")
#not the same!
>coxph(Surv(start,time,status)~x,data=aml4)
coef exp(coef) se(coef) z p
xNonmaintained 1.05 2.85 0.515 2.03 0.042
Likelihood ratio test=4.38 on 1 df, p=0.0363 n= 105
This one is corrrect
>aml5<-survSplit(aml,cut=c(5,9,10,12,40,50),end="time",start="start",event="status")
> coxph(Surv(start,time,status)~x,data=aml5)
coef exp(coef) se(coef) z p
xNonmaintained 0.916 2.5 0.512 1.79 0.074
Likelihood ratio test=3.38 on 1 df, p=0.0658 n= 103
It would be useful to modify survSplit to accomodate counting process
input as well.
Thanks
Danar
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Department of Statistics
Ume?? University
SE-90187 Ume??, Sweden