Hello all, I am trying to understand how to specify nested factors when using coxph(), and if it is appropriate to nest these factors in my situation. In the simplest form, I am testing two different temperatures, with each temperature being performed twice in different experimental periods (e.g. Temp5 performed in Period A and C, Temp4 performed in Period B and D) I am trying to see if survival time is affected by the treatment temperature. To do this I am using temperature and experimental period nested within temperature as factors.
> LOEtempmod.5days=coxph(LOE.stable.5days~Temp+Temp/Period,data=goodstable) Warning message: In coxph(LOE.stable.5days ~ Temp + Temp/Period, : X matrix deemed to be singular; variable 2 5 6 7 1. Is this an appropriate way of nesting? 2. Can this error message be ignored? Any help would be much appreciated, thank you in advance. Katie ______________________________________________ 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.
