Hi!
I have performed cox-regression on a data set with both continuous and categorical variables. In the cox-regr. command I specified categorical values by adding i. before variable. Shoenfeld residuals were saved by following command stcox i.spiders age i.sex i.ascites albumin bilirubi i.edema1 choleste i.stage,schoenfeld(sc*) scaledsch(ssc*). When assessing proportionality I used estat phtest, detail. All these went well. When I attempted to make plots with Schoenfeld residuals, I used estat phtest, plot(var) command which went well for continuous variables such as age, albumin etc., but when assessing categorical variables such as sex estat phtest, plot(sex), I got error response that this variable is not found in model. Could you give an advice what is wrong?