I have a data frame including various continuous variables (size of a lymph node measured in different ways) and an outcome (disease-free interval).
I have used the intcensROC package to assess the suitability of the size of the lymph node as a marker of disease-free interval with interval censored data.
U <- ASAC_tot$Left # left side of the interval censor data V <- ASAC_tot$Right # right side of the interval censor data Marker <- ASAC_tot$lymph.node.size # lymph node size Delta <- ASAC_tot$CENSOR_DFI # censuring status pTime <- 180 # to determine to predicted time res <- intcensROC (U, V, Marker, Delta, pTime, gridNumber = 500) head(res) auc <- intcensAUC(res) print(auc)
when I run this function, I end-up with the same AUC whatever the value of pTime...I find it strange...does anyone have any idea why ?
Also, even if I doubt there is a simple solution, is-there any way to determine a cut-off for the best lymph node size ? (no worries, the determination of the cut-off is ONLY to destroy its use :))