On 2012-08-29 08:45, S Ellison wrote:
id price distance
1 2 4
1 3 5
...
2 4 8
2 5 9
I would like to calculate the rank-order correlation between
price and distance for each id.
cor(price,distance,method = "spearman") calculate a
correlation for all.
Try by()
#Example
d <- data.frame(g=gl(5, 10), x=rnorm(50), y=rnorm(50))
by(d[,2:3], d$g, cor, method="spearman")
It may seem a bit of overkill, but the plyr package is handy and
gives a nice output:
library(plyr)
ddply(d, .(g), summarize, correlation = cor(x, y, method = 's'))
Peter Ehlers
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