From: Pascal BLEUYARD <p.bleuyard_at_opgc.univ-bpclermont.fr>

Date: Tue 22 Mar 2005 - 21:26:26 EST

Pascal BLEUYARD

Laboratoire de Météorologie Physique (LaMP) OPGC, Université Blaise Pascal

24, avenue des Landais

**63177 AUBIERE CEDEX
**

Tél : 04 73 40 73 75

Fax : 04 73 40 51 36

Mél : P.Bleuyard@opgc.univ-bpclermont.fr

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Mar 22 21:35:34 2005

Date: Tue 22 Mar 2005 - 21:26:26 EST

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 Météorologie Physique (LaMP) OPGC, Université Blaise Pascal

24, avenue des Landais

Tél : 04 73 40 73 75

Fax : 04 73 40 51 36

Mél : P.Bleuyard@opgc.univ-bpclermont.fr

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Mar 22 21:35:34 2005

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