On Tue, Aug 7, 2012 at 12:47 PM, Christopher R. Dolanc <crdol...@ucdavis.edu> wrote: > Hello, > > I have a data set that needs to be combined so that rows are summed by a > group based on a certain variable. I'm pretty sure rowsum() or rowsums() can > do this but it's difficult for me to figure out how it will work for my data > based on the examples I've read. > > My data are structured like this: > > Plot SizeClass Stems > 12 Class3 1 > 12 Class4 3 > 17 Class3 5 > 17 Class4 2 > > I simply want to sum the size classes by plot
Which variable do you want to sum? You'll want to use something like aggregate( XXX ~ YYY, data = dat.name, FUN = sum) to sum variable XXX by classes YYY. See ? aggregate for more details and worked examples. Cheers, Michael > and create a new data frame > with a size class called "Class34" or with the SizeClass variable removed. I > actually do have other size classes that I want to leave alone, but combine > 3 and 4, so if I could figure out how to do this by creating a new class, > that would be preferable. > > I've also attached a more detailed sample of data. > > Thanks, > Chris Dolanc > > -- > Christopher R. Dolanc > Post-doctoral Researcher > University of Montana and UC-Davis > > > ______________________________________________ > 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.
