C <- B C[A==0] <- 0 would be somewhat more efficient.
On Sun, 2 Mar 2008, jim holtman wrote:
Does this do what you want?A <- matrix(sample(0:2, 25, TRUE), ncol=5) B <- matrix(1:25, ncol=5) C <- ifelse(A == 0, 0, B) A[,1] [,2] [,3] [,4] [,5] [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 2B[,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 25C[,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 25On Sun, Mar 2, 2008 at 7:11 AM, Diogo André Alagador <[EMAIL PROTECTED]> 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@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@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.
-- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
______________________________________________ R-help@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.
