(This article was first published on [R] tricks, and kindly contributed to R-bloggers)
WelshPerm <- function(response,variable,nperm=999,...){
base <- oneway.test(response~variable,...)
base.p <- base$p.value
base.W <- base$statistic
count <- 1
# Permutation loop
for(i in 1:nperm){
SAMPLE <- sample(response)
welsh.perm<-oneway.test(SAMPLE~variable,...)
welsh.perm.p<-welsh.perm$p.value
welsh.perm.W<-welsh.perm$statistic if(abs(welsh.perm.W) >= abs(base.W)) {count <- count+1}
}
result=count/(nperm+1)
return(result)
}
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