On Sep 1, 2010, at 11:18 AM, <murali.me...@avivainvestors.com> wrote:
Hi folks,
I want to sort a matrix row-by-row and create a new matrix that
contains the corresponding colnames of the original matrix.
E.g.
set.seed(123)
a <- matrix(rnorm(20), ncol=4); colnames(a) <- c("A","B","C","D")
a
A B C D
[1,] -0.56047565 1.7150650 1.2240818 1.7869131
[2,] -0.23017749 0.4609162 0.3598138 0.4978505
[3,] 1.55870831 -1.2650612 0.4007715 -1.9666172
[4,] 0.07050839 -0.6868529 0.1106827 0.7013559
[5,] 0.12928774 -0.4456620 -0.5558411 -0.4727914
I want to obtain a matrix that looks like this
> t( apply(a, 1, function(x) colnames(a)[order(x)]) )
[,1] [,2] [,3] [,4]
[1,] "A" "C" "B" "D"
[2,] "A" "C" "B" "D"
[3,] "D" "B" "C" "A"
[4,] "B" "A" "C" "D"
[5,] "C" "D" "B" "A"
(apply returns a transposed version.)
A C B D
A C B D
D B C A
B A C D
C D B A
How best to achieve this? I was able to do it for the max and min of
each row by which.min, which.max, but for the entire thing, I'm
stymied.
--
David Winsemius, MD
West Hartford, CT
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