Thanks for all your help. Yes, it's very helpful.
Annie
On Thu, Sep 10, 2009 at 11:42 AM, Marc Schwartz <marc_schwa...@me.com>wrote:
> 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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