Dear all, I am using R 4.4.0 via RStudio (2024.04.0) on a Windows PC. The code below worked on the previous version of the flexsurv but is not working since my recent update (version 2.3). The code that was working is: library(survival) rfs <- pmax(rotterdam$recur, rotterdam$death) rfstime <- with(rotterdam, ifelse(recur==1, rtime, dtime)) fit1 <- flexsurvspline(Surv(rfstime, rfs) ~ age + meno + size + er, k=2, data = rotterdam) # obtain the linear predictor for each patient predf <- model.matrix(fit1) %*% fit1$res[-(1:4),"est"] # Predict baseline survival at 5 years y5_Flex_1 <- summary(fit1,type="survival",t=5) y5_Flex <- y5_Flex_1[[1]]$est y5_Flex # Shrinkage factor vanH <- 0.9589255 heuristic_lp_flex = vanH*predf?????? # Now calculate the shrunken model baseline survival prob at 5 years by fixing the shrunken lp as an offset and predicting the baseline survival fit1_shrunk <- flexsurvspline(Surv(rfstime,rfs)~offset(heuristic_lp_flex),k=2,data=rotterdam) The error message is Error in model.matrix.default(forms[[i]], m) : model frame and formula mismatch in model.matrix() Any suggestions gratefully received!!! Kind regards, Laura [[alternative HTML version deleted]]