Gallon, your question looks very homeworky. People on this list are not likely to help you unless you can demonstrate own effort (even if it failed), and the list is not for homework questions in case it is one. Where exactly are you stuck?
Daniel ------------------------- cuncta stricte discussurus ------------------------- -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of gallon li Sent: Wednesday, April 21, 2010 10:18 PM To: r-help Subject: [R] how to select the first observation only? 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]] ______________________________________________ [email protected] 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. ______________________________________________ [email protected] 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.
