1. I haven't seen that particular message before, so it is difficult to comment.
2. To go further, you will need to provide a reproducable example, i.e., some code/data that I could run to get the same error. 3. One note cox.NV <- coxph(Surv(recidivism$intDaysUntilFNVPO, recidivism$Event_nv) ~ recidivism$strGender + recidivism$intAgeAtMHCIndex + recidivism$PRE.nv + group + recidivism$MHC.nv + recidivism$SNFP , data = recidivism) would be much simpler to type as cox.NV <- coxph(Surv(intDaysUntilFNVPO, Event_nv) ~ strGender + intAgeAtMHCIndex + PRE.nv + group + MHC.nv + SNFP , data = recidivism) (That is one purpose of the data= argument, to make it simpler.) 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.