Hello, I am having some trouble with the 'censoring-adjusted C-index' by Uno et al, in the package survAUC. The relevant function is UnoC. The question has to do with what happens when I specify a time point t for the upper limit of the time range under consideration (we want to avoid using the right-end tail of the KM curve).
Copying from the example in the help file: TR <- ovarian[1:16,] TE <- ovarian[17:26,] train.fit <- coxph(Surv(futime, fustat) ~ age,x=TRUE, y=TRUE, method="breslow", data=TR) lpnew <- predict(train.fit, newdata=TE) Surv.rsp <- Surv(TR$futime, TR$fustat) Surv.rsp.new <- Surv(TE$futime, TE$fustat) If time is left NULL, the maximum futime in the TE data is assumed: UnoC(Surv.rsp, Surv.rsp.new, lpnew, time=NULL) #same as UnoC(Surv.rsp, Surv.rsp.new, lpnew, time=max(Surv.rsp.new[,1])) #which incidentally is the same as what one gets with the usual C-index function that also extends to the max event time. survConcordance(Surv.rsp.new ~ lpnew)$conc Now, if I specify a range times 'tau' (as in Table III of the relevant publication) I still get the same C for each timepoint: tau <- Surv.rsp.new[, 1] > tau [1] 1040 1106 1129 1206 1227 268 329 353 365 377 UnoC(Surv.rsp, Surv.rsp.new, lpnew, time=tau) [1] 0.7333333 0.7333333 0.7333333 0.7333333 0.7333333 0.7333333 0.7333333 0.7333333 0.7333333 0.7333333 #even worse, if I sort tau in ascending times I get 0's UnoC(Surv.rsp, Surv.rsp.new, lpnew, time=sort(tau)) [1] 0 0 0 0 0 0 0 0 0 0 This is a potentially very useful function so it would be great if someone could explain the behaviour here. Many thanks Eleni Rapsomaniki Research Associate/Statistician Strangeways Research Laboratory Department of Public Health and Primary Care University of Cambridge ______________________________________________ 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.
