Hello,
With the following, the first instruction will give you correlations
matrices, the second coefficients.
dat <- read.table(text = "
x y group
1 0.876751503 0.6518345 a
2 0.627067150 0.8801790 a
3 0.632465192 0.1768305 a
4 0.060359554 0.8835652 a
5 0.675868776 0.7721177 a
6 0.008465241 0.5046486 a
", header = TRUE)
str(dat)
lapply(split(dat[, c("x", "y")], dat$group), cor)
lapply(split(dat[, c("x", "y")], dat$group), function(d) cor(d$x, d$y))
Hope this helps,
Rui Barradas
Em 08-02-2013 16:33, carslaw escreveu:
I seem to have a Friday afternoon block and can't see the easiest way of
doing this.
Given a data frame like:
dat <- data.frame(x = runif(100), y = runif(100), group = rep(letters[1:10],
each = 10))
head(dat)
x y group
1 0.876751503 0.6518345 a
2 0.627067150 0.8801790 a
3 0.632465192 0.1768305 a
4 0.060359554 0.8835652 a
5 0.675868776 0.7721177 a
6 0.008465241 0.5046486 a
I want to work out cor(x, y) by group, so in this case ending up with 10
correlation coefficients by group.
I'm not seeing a straightforward solution and I'd appreciate your help.
Thanks
David
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