Hi all,
I need to compute some "occurence matrix": given a zero matrix and a set
of paired indexes, I want to store the number of occurences of each paired
index in a matrix. The paired indexes are stores as an index matrix. I
prefere not to use loops for performances purpose.
Here follows a dummy example:
> occurence <- matrix(0, 2, 2); data
[,1] [,2]
[1,] 0 0
[2,] 0 0
>
> index <- matrix(1, 3, 2); index
[,1] [,2]
[1,] 1 1
[2,] 1 1
[3,] 1 1
>
> occurence[index] <- occurence[index] + 1
I was expecting the folowing result:
> occurence
[,1] [,2]
[1,] 3 0
[2,] 0 0
I get instead:
> occurence
[,1] [,2]
[1,] 1 0
[2,] 0 0
I guess that there is some "hidden copy" involved but I wanted to know if
there is an efficient workaround (not using some loop structure). I thought
"factors" could do the job but I didn't manage to use them for that problem.
----------------------------------------------------------------------------
Pascal BLEUYARD
Laboratoire de M�t�orologie Physique (LaMP)
OPGC, Universit� Blaise Pascal
24, avenue des Landais
63177 AUBIERE CEDEX
T�l : 04 73 40 73 75
Fax : 04 73 40 51 36
M�l : [EMAIL PROTECTED]
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