Heinz Tuechler <[EMAIL PROTECTED]> writes: > Dear All, > > is there a stratified version of the Wilcoxon test (also known as van > Elteren test) available in R? > I could find it in the survdiff function of the survival package for > censored data. I think, it should be possible to use this function creating > a dummy censoring indicator and setting it to not censored, but may be > there is a better way to perform the test.
Not easily, I think. I played with the stratified Kruskal Wallis test (which is the same thing for larger values of 2...) with a grad student some years ago, but we never got it integrated as an "official" R function. It was not massively hard to code, as I recall it. Basically, you convert observations to within-stratum ranks, scaled so that the scores have similar variance (this is crucial: just adding the per-stratum rank sums won't work). You can then get the relevant SSD from lm(), by comparing the models "r ~ group + strata" and "r ~ strata". This SSD can be looked up as a chi-square statistic, possibly after applying a scale factor which I have forgotten.... (I.e. do your own math, don't trust me!) -- O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
