Look into merge() or, if you want to work at a lower level, match(). Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com
> -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf Of David Winsemius > Sent: Sunday, August 28, 2011 11:07 AM > To: Paul Hammer > Cc: r-help@r-project.org > Subject: Re: [R] comparing two unequal matrices without for loop? > > > On Aug 28, 2011, at 1:20 PM, Paul Hammer wrote: > > > Dear folks, > > > > I would like to compare two unequal matrices. > > "Unequal " is hardly an adequate data description. > > > At the moment I realize > > this with two for loop and an if function but that's definitely too > > slow > > :(... > > > > Here is my code: > > > > for (i in 1:length(all_expressed_genes[,1])) { > > for (j in 1:length(kegg_gene_pVal[,1])) { > > if (all_expressed_genes[j,1] == kegg_gene_pVal[i,1]) { > > kegg_gene_pVal[j,4] = all_expressed_genes[i,6] > > } > > } > > } > > > > Are there any faster solutions for that easy code? > > I'm trying to figure out what this is supposed to be doing. You are > making N^2 comparisons and transferring results from one vector of > length N to another vector of length N. Is this really what the (non- > existent) problem definition would have told us to do if you had > provided a problem definition? It appears there would be a great > possibility of overwriting earlier operations. And it appears to be > doing N^2-N unnecessary operations as well. > > > And why is R so > > dramatically slow when using for, while or other loop functions? > > Blaming the tool is generally a risky idea. Axes can be used > effectively or ineffectively. I'm guessing inadequate "operator" > training and/or confused problem specification. > > *---------------------* > > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > *---------------------* > > > David Winsemius, MD > West Hartford, CT > > ______________________________________________ > 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. ______________________________________________ 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.
