Try exact = TRUE: the default switches to a normal approximation that will not be adequate in your extreme example.
On Tue, 1 Jan 2008, Wolfgang Huber wrote: > When one of the two groups has only one member and the other one more > than 49, wilcox.test will exit with the below error message, > > n=51; wilcox.test(1:n ~ 1:n==1, conf.int=TRUE) > > Error in uniroot(wdiff, c(mumin, mumax), tol = 1e-04, zq = > qnorm(alpha/2, : > f() values at end points not of opposite sign > > > whereas with n=50 a result is returned: > > n=50; wilcox.test(1:n ~ 1:n==1, conf.int=TRUE) > > Wilcoxon rank sum test > > data: 1:n by 1:n == 1 > W = 49, p-value = 0.04 > alternative hypothesis: true location shift is not equal to 0 > 95 percent confidence interval: > 1 49 > sample estimates: > difference in location > 25 > > > I wonder whether it would be worthwhile to make the wilcox.test function > handle such (admittedly pathologic) cases more gracefully. > > > Happy New Year to all - > Wolfgang > > ------------------------------------------------------------------ > Wolfgang Huber EBI/EMBL Cambridge UK http://www.ebi.ac.uk/huber > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel