swh:1:snp:ff0951ca787d0b7f47dc2335f47fed43820a6324
Tip revision: 2ca0567606cfc5209c279478bd619238ac8f114f authored by Venkatraman E. Seshan on 27 April 2011, 00:00:00 UTC
version 0.9.7
version 0.9.7
Tip revision: 2ca0567
roc.area.test.Rd
\name{roc.area.test}
\title{Nonparametric area under the ROC curve}
\alias{roc.area.test}
\alias{print.roc.area.test}
\keyword{htest}
\description{
Computes the nonparametric area under the ROC curve and its variance
based on U-statistic theory (DDCP).
}
\usage{
roc.area.test(markers, status)
\method{print}{roc.area.test}(x, \dots)
}
\arguments{
\item{markers}{The marker values for each subject. If there are more
than one markers then this should be a matrix.}
\item{status}{binary disease status indicator}
\item{x}{object of class roc.area.test output from this function.}
\item{...}{optional arguments to the print function.}
}
\value{a list with the following elements
\item{area}{estimated area.}
\item{var}{estimated variance (matrix).}
\item{stat}{test statistic for equality of AUCs. Is not returned when
only one diagnostic marker is present.}
\item{p.value}{the p-value for the test of equality (2-sided).}
\item{df}{the degrees of freedom of the chi-square.}
The "print" method formats and returns the output.
}
\details{
It calculates the area and its variance. For more than one marker it
calculates the statistic to test for the equality of all AUCs. This
statistic has a standard normal reference distribution for two
variables and chi-square with number of variables minus 1.
}
\examples{
g <- rep(0:1, 50)
x <- rnorm(100) + g
y <- rnorm(100) + g
z <- rnorm(100) + g
roc.area.test(cbind(x,y), g)
roc.area.test(cbind(x,y,z), g)
y1 <- y + 0.75*g
roc.area.test(cbind(x,y1), g)
}
\references{
DeLong, E. R., D. M. DeLong, and D. L. Clarke-Pearson. 1988. Comparing
the areas under two or more correlated receiver operating characteristic
curves: A nonparametric approach. \emph{Biometrics} 44:837-845.
}