On Tue, 5 Jun 2007, baldeck wrote: > 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...
You haven't told us what form the 'data set' is, but I will presume a data frame called DF. The obvious first step is to split by Plot. Using 'resample' from ?sample sapply(with(DF, split(Tree, Plot)), resample, size=1) give a vector of trees ('individuals'?) with names the plots sampled from. That seems to be what you want, but if not please come back to us with a more extensive example including the desired output. > 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 > -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ 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.