> I'm new to R and am trying to fit a mixed model > Cox regression model with coxme function. > I have one two-level factor (treat) and one > covariate (covar) and 32 different groups > (centers). I'd like to fit a random coefficients model, with treat and covar > as fixed factors and a random intercept, random > treat effect and random covar slope per center. > I haver a couple of doubts on how to use coxme function for this task:
example deleted > * What if the treatment factor has more than two > levels. Should I follow the same procedure, with just bigger block sizes? > * Coxme returns a variance per each of the > variance matrices I defined, but no residual > variance estimate. Is there a way to get it? The coxme function does not support random slopes. It's been on my "to do" list for a long time. I am supposed to teach an American Stat Assoc course at the end of March, however, which has escalated the urgency. If the covariate has only 2 levels, such as a random treatment effect when there are only 2 treatments, then by coding the treatment as 0/1 and creating just the right covariates you could "trick" coxme into fitting the model. This is what is described in the report. You essentially make treatment a nested effect. fit1 <- coxme(Surv(y, uncens) ~ treat + covar, data1, random= ~1 | centers) fit2 <- coxme(Surv(y, uncens) ~ treat + covar, data1, random= ~1 | centers/treat) There is no residual variance for a Cox model. Your example was very hard to read. Consider using spaces, indentation, etc to make it easier for old eyes. Terry T. ______________________________________________ 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.