Re: [R] coxph and survfit issue - strata

From: Terry Therneau <>
Date: Mon, 09 May 2011 07:46:04 -0500

> Dear users,
> In a study with recurrent events:
> My objective is to get estimates of survival (obtained through a Cox
> model) by rank of recurrence and by treatment group.
> With the following code (corresponding to a model with a global
> effect of the treatment=rx), I get no error and manage to obtain
> what I want :
> data<-(bladder)
> model1<-coxph(Surv(stop,event)~rx+strata(enum)
> +cluster(id),data=bladder)
> data1<-data.frame(rx=1)
> survfit(model1,newdata=data1)
> But with the model with strata by treatment interaction
> (corresponding to a model with an effect of the treatment by rank),
> I get the following error:
> model2<-coxph(Surv(stop,event)~rx*strata(enum)
> +cluster(id),data=bladder)
> data1<-data.frame(rx=1)
> survfit(model2,newdata=data1)
> Erreur dans strata(enum) : objet "enum" non trouv? =>error in
> strata(enum) : object "enum" not found

 You have neglected to tell us what version of R and of the survival library you are using. (As the author, I always have the newest version of course.)

  The example you gave works if there is no "cluster" statement. Your error is a surprise to me and I will look into it.

 Terry Therneau mailing list PLEASE do read the posting guide and provide commented, minimal, self-contained, reproducible code. Received on Mon 09 May 2011 - 12:49:23 GMT

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