I tried this but did not work: z0<- by(z, z[,"n"], function(x) subset(x, sum(n==0)>2)) Peter Maclean Department of Economics UDSM
----- Original Message ---- From: Duncan Murdoch <murdoch.dun...@gmail.com> To: Peter Maclean <pmaclean2...@yahoo.com> Cc: r-help@r-project.org Sent: Wed, June 29, 2011 3:33:25 PM Subject: Re: [R] DROP OBSEVATION IN A GROUP On 29/06/2011 4:29 PM, Peter Maclean wrote: > People with more experience in R I need help on this. > I would like to drop observation if they meet certain condition. In this >example > I would like to drop group 2 in "n" because the group in "Y" has more than 2 > zeroes. > #Example > n<- c(1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3,3) > y<- c(2,3,2,3,4,5,6,1,0,0,0,6, 2, 1, 0, 0,9,3) > z<- as.data.frame(cbind(n,y)) > colnames(z)<- c("n","y") z0<- by(z, z[,"n"], function(x) subset(x, sum(n==0)>2)) The general way to drop observations is to construct a logical vector to use as an index. Entries which are FALSE are dropped. Doing that based on your "more than 2 zeroes" rule looks a little tricky; I think you want to count zeros first (e.g. using by()), then construct the TRUE/FALSE vector based on that. Duncan Murdoch > > > ______________________________________________ > 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.