[R] Wilcoxon Rank Sum in R with a multiple testing correction
mark_difford at yahoo.co.uk
Wed Nov 24 09:27:23 CET 2010
>> I'd like to use a Wilcoxon Rank Sum test to compare two populations of
>> values. Further, I'd like
>> to do this simultaneously for 114 sets of values.
Well, you read your data set into R using:
There are other ways to bring in data. Save the import to a workspace object
at the same time:
myDat <- read.csv (...)
Do the Wilcoxon Rank Sum tests using the implementation of your choice
(there are several):
## See the examples at foot of help page. Lacking data we will make some.
pv1 <- wilcox.test(rnorm(10), rnorm(10, 2), conf.int = TRUE)$p.value
pv2 <- wilcox.test(rnorm(10), rnorm(10, 2), conf.int = TRUE)$p.value
pv3 <- wilcox.test(rnorm(10), rnorm(10, 2), conf.int = TRUE)$p.value
Eventually you will discover more elegant ways of assembling a vector (or
some other type of storage object).
Finally, you feed your p-values to:
pAdj <- p.adjust (c(pv1, pv2, pv3), method = c("BH"))
cbind.data.frame (Uncorrected = c(pv1, pv2, pv3), BH_Corrected = pAdj)
Eventually you will discover how to turn all of this into an elegant
function. I really do hope that this is not a school assignment. If so....
Well, you still need to do some work to get this going.
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