Laura Rodriguez Murillo wrote: > Hi, > > I'm new in the mailing list but I would appreciate if you could help > me with this: > I have a big matrix from where I need to delete specific rows. The > second entry on these rows to delete should match any string within a > list (other file with just one column). > Thank you so much! > >
here's one way to do it, illustrated with dummy data: # dummy character matrix data = matrix(replicate(20, paste(sample(letters, 20), collapse="")), ncol=2) # filter out rows where second column does not match 'a' data[-grep('a', d[,2]),] this will work also if your data is actually a data frame: data = as.data.frame(data) data[-grep('a', d[,2]),] note, due to a known issue with grep, this won't work correctly if there are *no* rows that do *not* match the pattern: data[-grep('1', d[,2]),] # should return all of data, but returns an empty matrix with the upcoming version of r, grep will have an additional argument which will make this problem easy to fix: data[grep('a', d[,2], invert=TRUE),] vQ ______________________________________________ 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.