Try the duplicated() function. As in m[!duplicated(id), ]
-tgs On Wed, Apr 21, 2010 at 10:17 PM, gallon li <gallon...@gmail.com> wrote: > Dear r-helpers, > > I have a very simple question. Suppose my data is like > > id=c(rep(1,2),rep(2,2)) > b=c(2,3,4,5) > m=cbind(id,b) > > > m > id b > [1,] 1 2 > [2,] 1 3 > [3,] 2 4 > [4,] 2 5 > I wish to select the first observation for each id. That is, I want to > quickly select two rows: > > id b > 1 2 > 2 4 > > only. how should i do this? > > [[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. > [[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.
