How about %in% ?
# preparing something that looks like I think your data looks like: ap <- c("aajkss", "dfghjk", "sdfghk", "xxcvvn") af <- matrix(1:10, nrow=2) colnames(af) <- c("aajkss", "b", "c", "dfghjk", "e") # doing what I think you need done: ap[ap %in% colnames(af)] Cheers, B. (PS. a reproducible example saves us all time and unnecessary effort. :-) On May 8, 2015, at 3:50 PM, Kate Ignatius <kate.ignat...@gmail.com> wrote: > Hi, > > I have a list of 150 strings, say, ap,: > > aajkss > dfghjk > sdfghk > ... > xxcvvn > > > And I would l like to grep out these strings from column names in > another file, af,. I've tried the following but none seem to work: > > aps <- af[,grep(ap, colnames(af), value=TRUE)] > aps <- af[,grep(ap, colnames(af), value=FIXED)] > aps <- af[,grep(as.character(list(ap),colnames(af))] > > and also aps <- unique (grep(ap, colnames(af)) > > Is there another way I can do this - maybe without using grep? > > Thanks! > > Kate. > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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 -- To UNSUBSCRIBE and more, see 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.