\name{cindex.comp} \alias{cindex.comp} %- Also NEED an '\alias' for EACH other topic documented here. \title{Function to compare two concordance indices} \description{ This function compares two concordance indices computed from the same data by using the function \code{concordance.index}. The statistical test is a Student t test for dependent samples. } \usage{ cindex.comp(cindex1, cindex2) } %- maybe also 'usage' for other objects documented here. \arguments{ \item{cindex1}{first concordance index as returned by the \code{concordance.index} function.} \item{cindex2}{second concordance index as returned by the \code{concordance.index} function.} } \details{ The two concordance indices must be computed from the same samples (and corresponding survival data). The function uses a Student t test for dependent samples. } %%\note{ %%Since the comparison between the two concordance indices is done with a paired t-test that relies on the computation of the Pearson correlation coefficient between the original predictors \code{x}, any non-linear transformation of these predictors will affect the computation of the p-value. %%We are now using spearman correlation to circumvent this difficulty. %%} \value{ \item{p.value }{p-value from the Student t test for the comparison cindex1 > cindex2.} \item{cindex1 }{value of the first concordance index.} \item{cindex2 }{value of the second concordance index.} } \references{Haibe-Kains, B. and Desmedt, C. and Sotiriou, C. and Bontempi, G. (2008) "A comparative study of survival models for breast cancer prognostication based on microarray data: does a single gene beat them all?", \emph{Bioinformatics}, \bold{24}(19), pages 2200--2208.} \author{ Benjamin Haibe-Kains} %\note{ ~~further notes~~ } \seealso{\code{\link{concordance.index}}.} \examples{ set.seed(12345) age <- rnorm(100, 50, 10) size <- rexp(100,1) stime <- rexp(100) cens <- runif(100,.5,2) sevent <- as.numeric(stime <= cens) stime <- pmin(stime, cens) c1 <- concordance.index(x=age, surv.time=stime, surv.event=sevent, method="noether") c2 <- concordance.index(x=size, surv.time=stime, surv.event=sevent, method="noether") cindex.comp(c1, c2) } % Add one or more standard keywords, see file 'KEYWORDS' in the % R documentation directory. \keyword{survival} \keyword{htest}% __ONLY ONE__ keyword per line