Dear R users,
   
  Suppose that I generate the following :

  library(survival)
set.seed(123)
n=200 
x=rbinom(n,size=1,prob=0.5)
v=rep(rgamma(n/2,shape=1,scale=1),2)
w=rweibull(n,shape=1,scale=1)
b=-log(2)
t=exp(-x*b-log(v)+log(w))
c=rep(1,n)
id=rep(seq(1:(n/2)),2)
group=rep(1:(n/10),10)
fit2=coxph(Surv(t,c)~x+frailty(id,dist="gamma",sparce=T,method="em"))
   
  Using the command "fit2$frail" 
  I get the id level frailty terms ,
Some of the frailty terms are negative ,
 so Survival package gives not v but log(v)
Am I wrong ?

  best regards,
  D.Lalountas
University of Patras


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