Dear All, I am contemplating centering the covariates in my Cox model to reduce multicollinearity between the predictors and the interaction term and to render a more meaningful interpretation of the regression coefficient. Suppose I have two indicator variables, x1 and x2 which represent age categories (x1 is patients less than 16 while x2 is for patients older than 65). If I use the following Cox model, is there anyway I can centre the variables? Do I have to do it before I fit them into the model and if so, how?
fit2=coxph(Surv(rem.Remtime,rem.Rcens)~x1(partial)+x2(partial),data=partial,method="breslow") Thank you, Laura ______________________________________________ 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.
