I need to perform the Exact Wilcoxon Mann-Whitney on a subset of my database. Assuming that IPPO is my data frame and IPPOBIS is the subset my variable still have 3 different levels and the function wilcox_test (package "coin") does not accept it. I do not know how to overcome this problem.
ippo <- c(rep("A",10),rep("B",10),rep("C",10)) ippo2 <- c(rnorm(10,0,1),rnorm(10,10,10),rnorm(10,10,10)) IPPO <- data.frame(ippo,ippo2) IPPOBIS <- IPPO[IPPO$ippo == "A" | IPPO$ippo == "B",] wilcox_test(ippo2 ~ ippo,data=IPPOBIS,distribution=exact()) Error in check(itp) : 'object' does not represent a two sample problem levels(IPPOBIS$ippo) [1] "A" "B" "C" Massimo Cressoni ______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code.