one way is:
M <- matrix(sample(13, 9, TRUE), 3, 3)
n <- ncol(M)
ind <- apply(M, 2, which.max)
maxs <- M[cbind(ind, 1:n)]
diags <- diag(M)
diag(M) <- M[cbind(ind, 1:n)]
M[cbind(ind, 1:n)] <- diags
M
I hope it helps.
Best,
Dimitris
On 4/23/2010 10:10 PM, Jonathan wrote:
Hi r-help community,
This question isn't so much a syntax/coding one, but here goes:
Let's say I have matrix of arbitrary dimensions and I'd like to
reorder the rows in such a way that I could maximize the sum of the
entries along the diagonal.
For example, for this 3x3 matrix:
[,1] [,2] [,3]
[1,] 3 4 13
[2,] 9 1 2
[3,] 2 11 1
rearranging the rows to maximize the sum along the diagonal would
produce this matrix:
[,1] [,2] [,3]
[1,] 9 1 2
[2,] 2 11 1
[3,] 3 4 13
I've been experimenting with some scripts of my own, but I figured I'd
ask if one of you R-ninjas might know of an existing function (or
algorithm I could look up and then code) that can do this somewhat
efficiently (or even just correctly!).
Best,
Jonathan
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--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center
Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
