Hi If I understand correctly, use split and sample with lapply. If DF is your dataframe
lapply(split(DF$Tree, DF$Plot), function(x) sample(x,1)) shall select random tree from each plot. Or you can get it in tabular form with sapply. Regards Petr [EMAIL PROTECTED] napsal dne 05.06.2007 16:29:49: > > I have a data set of individual trees and the plots that they are in: > > Tree Plot > 56749 1 > 63494 1 > 87375 1 > 37494 2 > 92753 3 > 34847 3 > 38747 4 etc... > > So each plot is represented once for every individual that occurrs in it. > Plots get different numbers of rows because there can be a different number > of individuals in each plot. > > I want to make a data frame that consists of one individual from each plot. > I would like to randomly choose one individual from each plot that is > present in the data set. I will have to do this to multiple data sets which > may contain different plots, and may contain up to 1200 plots, so I can't > choose the plots by hand. > > Please help me with this. I'm an ecologist and I'm in Panama, with no one > around who is educated in R. Whoever solves this problem for me will be > acknowledged in any resulting publications. > > Thanks! > -Claire > -- > View this message in context: http://www.nabble.com/sampling-problem---new-to- > R-tf3872130.html#a10970708 > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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.