NonParametric.VUS.var: Boostrap variance of the nonparametric estimate on volumn...

In DiagTest3Grp: Diagnostic test summary measures for three ordinal groups

Description

Calculate the variance of the nonparametric estimate of volumn under ROC surface (VUS) through bootstrapping.

Usage

  NonParametric.VUS.var(x, y, z, alpha = 0.05, NBOOT = 100,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, confidence level for confidence interval, will result in (1-alpha)*100%; Default alpha=0.05, i.e., 95% confidence interval.
NBOOT	A numeric value, total number of bootstrap samples to draw for estimate of variance of the VUS nonparametric estimate.
FisherZ	A logic value. Default=FALSE. If TRUE, will transform the nonparametric estimate through Fisher's Z transformation: θ^*=1/2log(\frac{1+θ}{1-θ})

Details

Return a numeric value, the variance estimation on the nonparametric VUS estimate obtained through bootstrapping.

Value

Return a list of outputs, including,

variance	A numeric value, the estimate of variance of nonparametric VUS through bootstrapping.
lower	A numeric value, the lower limit of bootstrap basic quantile confidence interval for the estimate of variance of nonparametric VUS, i.e., (alpha/2)*100% quantile. Under default alpha=0.05, lower= basic 0.25% quantile of bootstrap variance estimates of the nonparametric VUS estimator.
upper	A numeric value, the upper limit of bootstrap basic quantile confidence interval for the estimate of variance of nonparametric VUS, i.e., (1-alpha/2)*100% quantile. Under default alpha=0.05, upper= basic 0.975% quantile of bootstrap variance estimates of the nonparametric VUS estimator.

Warning

The bootstrap variance estimate may take a minute.

Note

Bug reports, malfunctioning, or suggestions for further improvements or contributions can be sent to Jingqin Luo <[e-mail]>.

Author(s)

Jingqin Luo

References

Bradley Efron, Robert Tibshirani, Robert J. Tibshirani (1993) An introduction to the bootstrap CRC Press.

See Also

VUS Normal.VUS Youden3Grp.Variance.Bootstrap

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.var (x=x, y=y, z=z, alpha=0.05, NBOOT=10)

DiagTest3Grp documentation built on April 14, 2017, 5:53 p.m.