Dear R-help, I have to calculate the percent inclusion of each variable in a bootstrap validation of a cox proportional hazards model(described in Sauerbrei and Schumacher, Stat Med 11:1093, 1992).
First I need to get a bootstrap sample from my dataset, which I did with the sample function. Then I tried to run a cph model and looked which covariates are significant. This I would repeat 200 times and at the end calculate how many percent the covariates were included. This is what I entered: boot1 <- sample(Dataset, 300, replace=T) cph1 <- cph(Surv(months,status) ~ cov1 + cov2 + cov3 + cov4, data=boot1) Unfortunately, I get exactly the same results (coefficient, SE, p-value) then when I would fit a Cox model without drawing a bootstrap sample before. How do I do it right? Or is there another way to calculate the percentage? Sorry for my bad English. Thanks. Dott. Mario Rossi University of Foggia, Italy ______________________________________________ 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.
