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
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