Hello everyone, I have been trying to use the timedep(predictor) capability of the frailtypack package in order to include time-varying covariates in a frailty model. The following is an example of the code I use: sha.time <- frailtyPenal(Surv(time,event)~cluster(id)+timedep(age) ,Frailty=TRUE,data=StudyData,n.knots=8,kappa1=1) However, I get the following error message when running the above code. Error in eval(expr, envir, enclos) : could not find function "timedep" I do get model parameter estimates when I remove timedep() from the syntax. Thanks in advance for your help and pointers