Hi: You need a leading ^ in your grep string. Here's a reproducible example to illustrate:
df <- data.frame(Xyz1 = rnorm(5), Xyz2 = rnorm(5), Xyz3 = rnorm(5), Abc1 = rnorm(5), Abc2 = rnorm(5)) df[, grep('^Xyz', names(df))] df[, grep('^Abc', names(df))] HTH, Dennis On Mon, Aug 22, 2011 at 7:33 AM, Jay <josip.2...@gmail.com> wrote: > Hi, > > Let's say that I have a set of column names that begin with the string > "Xyz". How do I extract these specific columns? I tried to do the > following: > > dataframe1[,grep("Xyz",colnames(dataframe1))] > > But it does not work. What is wrong with my expression? > > ______________________________________________ > 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.