Hello, I used PBC data set included in the "survival" package to fit a cox model. The model included a restricted cubic spline transformation on age. Then I tried using "survfit" function to predict a survival curve using the first row of the original data. I got an error message. The R code and error message is below.
> require(survival) > fit<-coxph(Surv(time,status==2)~rcs(age,4)+sex, data=pbc) > id1<-pbc[1,] > surv.id1<-survfit(fit,newdata=id1) Error in rcspline.eval(x, nk = nknots, inclx = TRUE, pc = pc) : fewer than 6 non-missing observations with knots omitted Can anyone provide any suggestions? Thanks, Zhiyuan ______________________________________________ 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.