Sorry, correction below.
Peter Ehlers wrote:
Kim Vanselow wrote:
Dear r-helpers,
I want to test groups of samples for significant differences.
Question: Does Group1 differ significantly from group2.
This is a question to be answered by mann-whitney-u-test.
I know that I can use wilcox.test with 2 samples.
My problem: How can r perform the test automatically if there are more
than 2 groups in my data frame.
Test group1 vs. 2, 1 vs. 3, 1 vs. 4, etc.
This is my skript:
Deckung <- read.table("Gesamtdeckung.csv", sep=";", header=TRUE,
dec=",", row.names=1)
x <- Deckung$Gesamtdeckung
y <- Deckung$Klasse
#U-Test
wilcox.test(x ~ y, paired = FALSE, subset = y %in% c("1", "2"))
wilcox.test(x ~ y, paired = FALSE, subset = y %in% c("1", "3"))
wilcox.test(x ~ y, paired = FALSE, subset = y %in% c("2", "3"))
Any help would be greatly appreciated!
Thanks
Kim
This sounds like serious data dredging, but if you're
sure that it's what you want, try the combn() function:
y <- gl(4, 5)
x <- rnorm(20)
m <- cbind(t(combn(4, 2)), NA)
for(i in 1:nrow(idx))
m[i, 3] <-
wilcox.test(x ~ y, subset = y %in% idx[i,])$p.value
m
-Peter Ehlers
y <- gl(4, 5)
x <- rnorm(20)
m <- cbind(t(combn(4, 2)), NA)
for(i in 1:nrow(m)) # change 'idx' to 'm'
m[i, 3] <-
wilcox.test(x ~ y, subset = y %in% m[i,])$p.value # ditto
-Peter Ehlers
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