If you want count: xtabs( ~ x + y, X)
or sum: xtabs(z ~ x + y, X) On Tue, Jan 25, 2011 at 5:25 PM, Ryan Utz <utz.r...@gmail.com> wrote: > Hi R-users, > > I'm trying to find an elegant way to count the number of rows in a > dataframe > with a unique combination of 2 values in the dataframe. My data is > specifically one column with a year, one with a month, and one with a day. > I'm trying to count the number of days in each year/month combination. But > for simplicity's sake, the following dataset will do: > > x<-c(1,1,1,1,2,2,2,2,3,3,3,3) > y<-c(1,1,2,2,3,3,4,4,5,5,6,6) > z<-c(1,2,3,4,5,6,7,8,9,10,11,12) > X<-data.frame(x y z) > > So with dataset X, how would I count the number of z values (3rd column in > X) with unique combinations of the first two columns (x and y)? (for > instance, in the above example, there are 2 instances per unique > combination > of the first two columns). I can do this in Matlab and it's easy, but since > I'm new to R this is royally stumping me. > > Thanks, > Ryan > > -- > Ryan Utz > Postdoctoral research scholar > University of California, Santa Barbara > (724) 272 7769 > > [[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. > -- Henrique Dallazuanna Curitiba-Paraná-Brasil 25° 25' 40" S 49° 16' 22" O [[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.
