Hi, I am using clogit() from survival package to do conditional logistic regression. I also need to make prediction on an independent dataset to calculate predicted probability. Here is an example:


> dat <- data.frame(set=rep(1:50,each=3), status=rep(c(1,0,0),50), x1=rnorm(150,5,1), x2=rnorm(150,7,1.5))
> dat.test <- data.frame(set=rep(1:30,each=3), status=rep(c(1,0,0),30), x1=rnorm(90,5,1), x2=rnorm(90,7,1.5))
> fit<-clogit(status~x1+x2+strata(set),dat)
> predict(fit,newdata=dat.test,type='expected')
Error in Surv(rep(1, 150L), status) : 
  Time and status are different lengths

Can anyone suggest what's wrong here?

Thanks!

John
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