Dear Julia, Try this: DF<-read.table(textConnection(" x1 x2 x3 1 2 3 4 5 6 7 8 9"),header=TRUE) closeAllConnections()
DF$x4<-DF$x1+DF$x2 DF HTH, Jorge On Tue, Jan 20, 2009 at 2:12 PM, Julia Zhou <ms.juliaz...@gmail.com> wrote: > Hi, > > I would like to operate on certain columns in a dataframe, but not > others. My data looks like this: > > x1 x2 x3 > 1 2 3 > 4 5 6 > 7 8 9 > > I want to create a new column named x4 that is the sum of x1 and x2, > but NOT x3. I looked at colSums and apply, but those functions seem to > use all the columns in a dataframe. How do I only use select columns? > > If it helps, in Stata this would be gen x4 = x1 + x2. > > Thanks! > > ______________________________________________ > 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. > [[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.