roc.perm.test: Permutation test to compare ROC curve
Description
Computes the test statistic and permutation reference distribution for
comparing paired or unpaired ROC curves.
Usage
roc.perm.test(marker, status, marker2=NULL, group=NULL,
nperm=2500, mp=NULL)
# S3 method for roc.perm.test
print(x, ...)
# S3 method for roc.perm.test
plot(x, ...)
Value
an object of class roc.perm.test with the following elements
ostat
test statistic from the observed data.
pstat
test statistic from permuted data.
p.value
the p-value for the test of equality (2-sided).
The "print" method formats and returns the statistic and p-value.
The "plot" method plots the density from the permutation reference
distribution and marks the location of the observed statistic.
Arguments
marker
marker values for each subject.
status
binary disease status indicator.
marker2
second diagnostic marker for the same subjects (paired).
group
indicator of which diagnostic test was used (unpaired).
nperm
number of permutations for the reference distribution.
mp
mixing proportion for the unpaired case when proportion of
diseased subjects can differ.
x
object of class roc.perm.test output from this function.
...
optional arguments to print and plot functions.
Details
This function implements the permutation method described in the
Venkatraman and Begg (1996) paper for the paired case and the
Venkatraman (2000) paper for the unpaired case.
The function detects whether the data are paired or unpaired by
testing which of the options marker2 and group is specified. If both
are missing it will stop with an error message. At present exactly
one should be missing.
References
Venkatraman, E.S. and Begg, C.B. (1996). A distribution-free procedure
for comparing receiver operating characteristic curves from a paired
experiment. Biometrika 83, 835-848.
Venkatraman, E.S. (2000) A permutation test to compare receiver
operating characteristic curves. Biometrics 56(4):1134-8.