# [R] loop problem

Dimitris Rizopoulos dimitris.rizopoulos at med.kuleuven.be
Mon Dec 5 16:54:39 CET 2005

```you could consider something like this:

A <- matrix(rnorm(100 * 3), 100, 3); colnames(A) <- letters[1:3]
B <- matrix(rnorm(100 * 5), 100, 5); colnames(B) <- letters[4:8]
####
z <- matrix( 0, ncol(A), ncol(B), dimnames = list(colnames(A),
colnames(B)) )
for(i in 1:ncol(A)){
z[i, ] <- apply(B, 2, function(x, y) cor.test(x, y)\$p.value, y =
A[, i])
}
z

I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://www.med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm

----- Original Message -----
From: "Frank Johannes" <fjohannes at fastmail.fm>
To: <r-help at stat.math.ethz.ch>
Sent: Monday, December 05, 2005 4:28 PM
Subject: [R] loop problem

> Hi,
> Here is my problem. Say I have two matrices,
>
> Matrix A:
>
> a b c
> 4 5 2
> 3 2 1
> 4 5 6
>
> Matrix B:
> d e f g h
> 3 4 5 2 1
> 2 3 7 8 6
> 8 5 1 3 4
>
> I would like to correlate vector a of matrix A with with vectors
> d,e,f,g,h of
> matrix "B" and save the p-values (or some type of statistic) in a
> seperate result vector, say z. Then, I would like to repeat this
> process
> for vector b and vector c of matrix A. In the present example,
> vector z
> would end up containg 15 elements.
> I tried a few double loops, but was not successful in saving the
> results
> in a vector. I was only able to print them with the "print" or "cat"
> command, but could not turn the print or cat results into an
> accessible
> object.
>
> Help would be appreciated.
> Thank you,
> Frank.
>
> --
>
>                          or over the web
>
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