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.