multivariate version of aggregate

You can pass a matrix to by()

set.seed(42)
dat <- data.frame(x=runif(50)*20, y=runif(50)*20,

g=rep(LETTERS[1:2], each=25))

as.vector(by(dat[,1:2], dat$g, function(x) cor(x)[1,2]))

[1] -0.05643063  0.16465040

-------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77840-4352

-----Original Message-----
From: r-help-bounces at r-project.org
[mailto:r-help-bounces at r-project.org] On Behalf Of Jannis
Sent: Thursday, June 27, 2013 12:27 PM
To: r-help
Subject: [R] multivariate version of aggregate

Dear List members,


i am seeking a multivariate version of aggregate. I want to compute,
fro 
example the correlation between subsets of two vectors. In
aggregate, i 
can only supply one vector with indices for subsets. Is  there ready

function for this or do i need to program my own?


Cheers
Jannis

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