Hi william, Now it is very fast. Thanks for you and also for David for your time.
cheers milton On Wed, Aug 26, 2009 at 3:48 PM, William Dunlap <wdun...@tibco.com> wrote: > > > Bill Dunlap > TIBCO Software Inc - Spotfire Division > wdunlap tibco.com > > > -----Original Message----- > > From: r-help-boun...@r-project.org > > [mailto:r-help-boun...@r-project.org] On Behalf Of milton ruser > > Sent: Wednesday, August 26, 2009 9:54 AM > > To: r-help@r-project.org > > Subject: [R] changing equal values on matrix by same random number > > > > Dear all, > > > > I have about 30,000 matrix (512x512), with values from 1 to N. > > Each value on a matrix represent a habitat patch on my > > matrix (i.e. my landscape). Non-habitat are stored as ZERO. > > No I need to change each 1-to-N values for the same random > > number. > > > > Just supose my matrix is: > > mymat<-matrix(c(1,1,1,0,0,0,0,0,0,0,0, > > 0,0,0,0,2,2,2,0,0,0,0, > > 0,0,0,0,2,2,2,0,0,0,0, > > 3,3,0,0,0,0,0,0,0,4,4, > > 3,3,0,0,0,0,0,0,0,0,0), nrow=5) > > > > I would like that all cells with 1 come to be > > runif(1,min=0.4, max=0.7), and cells with 2 > > be replace by another runif(...). > > > > I can do it using for(), but it is very time expensive. > > Any help are welcome. > > Is the following what you want? It uses the small > integers in mymat as indices into a vector of N random > numbers. > > > mymat > [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] > [1,] 1 0 0 2 0 0 0 0 0 3 0 > [2,] 1 0 0 2 0 2 0 0 0 0 0 > [3,] 1 0 0 2 0 2 0 0 4 0 0 > [4,] 0 0 0 0 0 2 3 0 4 0 0 > [5,] 0 0 0 0 0 0 3 0 3 0 0 > > range(unique(mymat)) > [1] 0 4 > > f<-function(mat){ > N<-max(mat) > tmp <- mat[mat>0] > tmp <- runif(N, 0.4, 0.7)[tmp] > mat[mat>0] <- tmp > mat > } > > f(mymat) > [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] > [,9] > [1,] 0.5361427 0 0 0.6727491 0 0.0000000 0.0000000 0 > 0.0000000 > [2,] 0.5361427 0 0 0.6727491 0 0.6727491 0.0000000 0 > 0.0000000 > [3,] 0.5361427 0 0 0.6727491 0 0.6727491 0.0000000 0 > 0.5357566 > [4,] 0.0000000 0 0 0.0000000 0 0.6727491 0.6417832 0 > 0.5357566 > [5,] 0.0000000 0 0 0.0000000 0 0.0000000 0.6417832 0 > 0.6417832 > [,10] [,11] > [1,] 0.6417832 0 > [2,] 0.0000000 0 > [3,] 0.0000000 0 > [4,] 0.0000000 0 > [5,] 0.0000000 0 > > The 3 lines involving tmp could be collapsed into one, making > things more obscure > mat[mat>0] <- runif(N, 0.4, 0.7)[mat[mat>0]] > > Bill Dunlap > TIBCO Software Inc - Spotfire Division > wdunlap tibco.com > > > cheers > > > > milton > > > > [[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<http://www.r-project.org/posting-guide.html> > > and provide commented, minimal, self-contained, reproducible code. > > > [[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.
