The best way to get an answer is to provide sample data and desired results (computed by hand or by any other available means). See http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example.
In the vague question begets a vague answer department, I would use melt from the reshape package, and make some columns that contain unique key values for each time interval, and then use aggregate or ddply from the plyr package. --------------------------------------------------------------------------- Jeff Newmiller The ..... ..... Go Live... DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go... Live: OO#.. Dead: OO#.. Playing Research Engineer (Solar/Batteries O.O#. #.O#. with /Software/Embedded Controllers) .OO#. .OO#. rocks...1k --------------------------------------------------------------------------- Sent from my phone. Please excuse my brevity. Keith Weintraub <kw1...@gmail.com> wrote: >Folks, > I have a data frame with columns 200401, 200402, ..., 201207, 201208. > >These represent years/months. What would be the best way to sum these >columns by year? What about by quarter? > >Thanks for your time, >KW > >-- > > > [[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. ______________________________________________ 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.