Or, more general (if you need to include more than just one variable from TestData), something like
by(TestData, LEAID, function(x) median(x$RATIO)) Agreed, this is less appealing for the given example than Ista's code, but might help to better understand by and to generalize its use to other situations. Michael > -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of Ista Zahn > Sent: Mittwoch, 9. Dezember 2009 02:54 > To: L.A. > Cc: r-help@r-project.org > Subject: Re: [R] by function ?? > > Hi, > I think you want > > by(TestData[ , "RATIO"], LEAID, median) > > -Ista > > On Tue, Dec 8, 2009 at 8:36 PM, L.A. <ro...@millect.com> wrote: > > > > I'm just learning and this is probably very simple, but I'm stuck. > > I'm trying to understand the by(). > > This works. > > by(TestData, LEAID, summary) > > > > But, This doesn't. > > > > by(TestData, LEAID, median(RATIO)) > > > > > > ERROR: could not find function "FUN" > > > > HELP! > > Thanks, > > LA > > -- > > View this message in context: > > http://n4.nabble.com/by-function-tp955789p955789.html > > Sent from the R help mailing list archive at Nabble.com. > > > > ______________________________________________ > > 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. > > > > > > -- > Ista Zahn > Graduate student > University of Rochester > Department of Clinical and Social Psychology http://yourpsyche.org > > ______________________________________________ > 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.