On Nov 13, 2007 5:53 AM, Shoaaib Mehmood <[EMAIL PROTECTED]> wrote: > i want to make survival plots for a coxph object using survfit > function. mod.phm is an object of coxph class which calculated results > using columns X and Y from the DataFrame. Both X and Y are > categorical. I want survival plots which shows a single line for each > of the categories of X i.e. '4' and 'C'. I am getting the following > error: > > > attach(DataFrame) > > DataFrame.X<-data.frame(X=c('4','C'),Y=rep(mean(Y),2)) > > detach()
As you have it, Y in DataFrame.X will be created as numeric which isn't what you probably want (since you say Y is categorical). Also, you will run into problems if you create newdata and it doesn't have all the levels of all the factors in your model. You can do this: newdat <- expand.grid(X = c("4", "C", plus all other levels), Y = c("2", plus all other levels)) plot(survfit(cox.mod, newdata = subset(newdat, Y == "2"))) > > plot(survfit(mod.phm, newdata=DataFrame.X), lty=c(1,2),ylim=c(.6,1)) > Error in `contrasts<-`(`*tmp*`, value = "contr.treatment") : > contrasts can be applied only to factors with 2 or more levels > > any help will be appreciated. > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.