You have (unimportant lines omitted) > c2= survdiff(Surv(act.surv.time,censoring)~treatgrp ,data=b) > plot(c2) The problem is that you are using the wrong function. It is survfit that creates plottable survival curves, survdiff only does the log-rank test. Terry Therneau
______________________________________________ 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.