On Sep 10, 2009, at 1:34 PM, annie Zhang wrote:
Hi, All,
How can I get the indices of the minimum elements in a matrix
without using
a loop?
For example, if the matrix is
4 5 2
2 8 9
5 2 3
Then I want to output (1,3), (2,1), (3,2).
Thanks,
Annie
mat <- matrix(c(4, 2, 5, 5, 8, 2, 2, 9, 3), 3)
> mat
[,1] [,2] [,3]
[1,] 4 5 2
[2,] 2 8 9
[3,] 5 2 3
> which(mat == min(mat), arr.ind = TRUE)
row col
[1,] 2 1
[2,] 3 2
[3,] 1 3
See ?which and take note of the arr.ind argument.
HTH,
Marc Schwartz
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