From: Torsten Hothorn <Torsten.Hothorn_at_rzmail.uni-erlangen.de>

Date: Tue 30 Aug 2005 - 19:42:40 EST

T = 0.5242, df = 2, p-value = 0.7694

T = 0.3824, df = 2, p-value = 0.826

T = 0.0264, df = 1, p-value = 0.871

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Aug 30 19:48:47 2005

Date: Tue 30 Aug 2005 - 19:42:40 EST

On Mon, 29 Aug 2005, Peter Dalgaard wrote:

> Torsten Hothorn <Torsten.Hothorn@rzmail.uni-erlangen.de> writes:

*>
**> > > Dear All,
**> > >
**> > > is there a stratified version of the Wilcoxon test (also known as van
**> > > Elteren test) available in R?
**> >
**> > you can plug it together using the `coin' infrastructure (see the
**> > examples in the manual and vignette).
**>
**> I managed to dig out our old code, and patched it up loosely to fit
**> versions of R later than 0.62 (the trend test code still seems
**> broken). Use at own risk. The usage is fairly straightforward:
**>
**> > SKruskal.test(y~g1|g2)
**>
**> Kruskal-Wallis stratified rank sum test
**>
**> data: y , group: g1 , strata: g2
**> K = 3.1486, df = 3, p-value = 0.3693
**>
*

the conditional version of the above test can be computed as follows:

R> library("coin") R> set.seed(290875) R> mydf <- data.frame(y = rnorm(90), x = gl(3, 30)[sample(1:90)], b = gl(3, 30)) R> R> ### with global ranks, i.e., ranking without using the blocks R> kruskal_test(y ~ x | b, data = mydf) Asymptotic Kruskal-Wallis Test data: y by groups 1, 2, 3 stratified by b

T = 0.5242, df = 2, p-value = 0.7694

R> R> ### with _blockwise_ ranking and quadratic form of the test statistic R> independence_test(y ~ x | b, data = mydf, ytrafo = function(data) trafo(data, + numeric_trafo = rank, block = mydf$b), teststat = "quad") Asymptotic General Independence Test data: y by groups 1, 2, 3 stratified by b

T = 0.3824, df = 2, p-value = 0.826

R> R> ### the same R> SKruskal.test(y ~ x | b, data = mydf) Kruskal-Wallis stratified rank sum test

data: y , group: x , strata: b

K = 0.3824, df = 2, p-value = 0.826

R> R> R> R> ### trend test (using scores 1, 2, 3) R> independence_test(y ~ x | b, data = mydf, ytrafo = function(data) trafo(data, + numeric_trafo = rank, block = mydf$b), teststat = "quad", + scores = list(x = 1:3)) Asymptotic General Independence Test data: y by groups 1 < 2 < 3 stratified by b

T = 0.0264, df = 1, p-value = 0.871

R> R> ### hm. R> SKruskal.test(y ~ x | b, data = mydf, trend = TRUE) Error in SKruskal.test(y ~ x | b, data = mydf, trend = TRUE) : subscript out of bounds

Best,

Torsten

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Aug 30 19:48:47 2005

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