[R] reordering of matrix rows to maximize the sum of the diagonal
David Winsemius
dwinsemius at comcast.net
Fri Apr 23 22:20:24 CEST 2010
Can you specify how you would re-order this matrix:
matrix(1:16, 4,4)
> apply(mtx, 2, which.max)
[1] 4 4 4 4
--
David.
On Apr 23, 2010, at 4:10 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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David Winsemius, MD
West Hartford, CT
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