DiagTest3Grp (version 1.6)

NonParametric.VUS: Nonparametric estimate of volumn under ROC surface (VUS)

Description

Nonparametric estimate of volumn under ROC surface (VUS)

Usage

NonParametric.VUS(x, y, z,alpha=0.05,NBOOT=50,FisherZ=FALSE)

Arguments

x

A numeric vector, a diagnostic test's measurements in the $D^-$ (usually healthy subjects).

y

A numeric vector, a diagnostic test's measurements in the $D^0$ (usually mildly diseased subjects).

z

A numeric vector, a diagnostic test's measurements in the $D^+$ (usually severely diseased subjects).

alpha

A numeric value, (1-alpha)*100% percentile Confidence interval of the VUS estimate under normal assumption. Default, alpha=0.05.

NBOOT

A integer.Total number of bootstrap samples for implementation.

FisherZ

A logic value. Default=FALSE. If TRUE, will transform the nonparametric estimate through Fisher's Z transformation: $\theta^*=1/2log(\frac{1+\theta}{1-\theta})$

Value

Return a numeric value as the nonparametric estimate of the VUS.

Details

The volume under ROC surface (VUS) indicates the probability of correctly ranking a randomly selected triplet $(U,V,W)$ of a diagnostic test's measurements, each from $D^-$,$D^0$,$D^+$, i.e., $VUS=Pr\{U

References

Xiong, C. and van Belle, G. and Miller, J.P. and Morris, J.C. (2006) Measuring and Estimating Diagnostic Accuracy When There Are Three Ordinal Diagnostic Groups. Statistics In Medicine 25 7 1251--1273.

Ferri, C. and Hernandez-Orallo, J. and Salido, M.A. (2003) Volume under the ROC Surface for Multi-class Problems LECTURE NOTES IN COMPUTER SCIENCE 108--120.

See Also

VUS Normal.VUS NonParametric.VUS.var

Examples

 data(AL)
 group <- AL$group
 table(group)

 ##take the negated FACTOR1 marker measurements
 factor1 <- -AL$FACTOR1

 x <- factor1[group=="D-"]
 y <- factor1[group=="D0"]
 z <- factor1[group=="D+"]

 nonpar.vus <- NonParametric.VUS(x=x,y=y,z=z)