From: jim holtman <jholtman_at_gmail.com>

Date: Sun, 02 Mar 2008 07:18:50 -0500

[4,] 4 9 14 19 24

[5,] 5 10 15 20 25

*> C
*

*>
*

Date: Sun, 02 Mar 2008 07:18:50 -0500

[1,] 1 1 1 2 1 [2,] 1 0 1 1 0 [3,] 0 0 1 0 2 [4,] 0 1 2 0 0 [5,] 1 2 1 2 2

> B

[,1] [,2] [,3] [,4] [,5] [1,] 1 6 11 16 21 [2,] 2 7 12 17 22 [3,] 3 8 13 18 23

[4,] 4 9 14 19 24

[5,] 5 10 15 20 25

[,1] [,2] [,3] [,4] [,5]

[1,] 1 6 11 16 21 [2,] 2 0 12 17 0 [3,] 0 0 13 0 23 [4,] 0 9 14 0 0 [5,] 5 10 15 20 25

On Sun, Mar 2, 2008 at 7:11 AM, Diogo André Alagador
<mcnda839_at_mncn.csic.es> wrote:

> To all,

*>
**>
**>
**> I am undergoing an analysis involving big matrices of about 30000x200 which
**> I have to handle in a more efficient way. So I would like some advice to
**> build such efficient function to deliver the following result:
**>
**>
**>
**> - starting with 2 matrices of the same dimension (eg. A and B)
**>
**>
**>
**> 0 0 3 5 6 0 0 5
**>
**> A= 0 0 6 4 B= 0 4 3 5
**>
**> 0 0 5 0 1 0 0 9
**>
**>
**>
**> - the function should deliver a C matrix (same dimension too),
**> where at each position C(i,j), compares A and B.
**>
**> if A(i,j)=0, than C(i,j)=0,
**>
**> if A(i,j)!=0, than C(i,j)=B(i,j)
**>
**>
**>
**> 6 0 0 5
**>
**> C= 0 0 3 5
**>
**> 0 0 0 0
**>
**>
**>
**> Although not an expert I could build a function with 2 cycles (reading
**> columns and rows) which is not quick. Maybe you can help me in this
**> "challenge".
**>
**>
**>
**> Much thanks in advance,
**>
**>
**>
**>
**> Diogo André Alagador
**> Biodiversity & Global Change Lab, Museo Nacional de Ciencias Naturales,
**> CSIC, Madrid, España
**> Forest Research Centre, Instituto Superior de Agronomia, Universidade
**> Técnica de Lisboa, Lisboa, Portugal
**>
**>
**> [[alternative HTML version deleted]]
**>
**>
**> ______________________________________________
**> R-help_at_r-project.org mailing list
**> https://stat.ethz.ch/mailman/listinfo/r-help
**> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
**> and provide commented, minimal, self-contained, reproducible code.
**>
**>
*

-- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? ______________________________________________ R-help_at_r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.Received on Sun 02 Mar 2008 - 12:20:58 GMT

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