thank you, william and bill. wow, this was fast. I have been tearing my hair out over this one, trying to work the wrong tool. (this would make a good "see also" in the "by" function.) ---- Ivo Welch (ivo.we...@brown.edu, ivo.we...@gmail.com)
On Mon, Mar 21, 2011 at 7:09 PM, William Dunlap <wdun...@tibco.com> wrote: >> -----Original Message----- >> From: r-help-boun...@r-project.org >> [mailto:r-help-boun...@r-project.org] On Behalf Of ivo welch >> Sent: Monday, March 21, 2011 3:43 PM >> To: r-help >> Subject: [R] Merging by() results back into original data frame? >> >> dear R experts---I am trying to figure out what the recommended way is >> to merge by() results back into the original data frame. for example, >> I want to have a flag that tells me whether a particular row contains >> the maximum for its group. >> >> d <- data.frame(group=as.factor(rep(1:3,each=3)), val=rnorm(9)) > > ave() could do what you want without using by(). E.g., > > > d$isGroupMax <- with(d, ave(val, group, FUN=max) == val) > > d > group val isGroupMax > 1 1 0.21496662 FALSE > 2 1 -1.44767939 FALSE > 3 1 0.39635971 TRUE > 4 2 0.60235172 FALSE > 5 2 0.94581401 TRUE > 6 2 0.01665084 FALSE > 7 3 -0.58277312 FALSE > 8 3 0.82930370 FALSE > 9 3 1.02906920 TRUE > > Bill Dunlap > Spotfire, TIBCO Software > wdunlap tibco.com > >> highestvals <- by( d, d$group, function(d)(max(d$val)) ) >> >> ## and now? iterate over levels( d$group ) ? how do I merge >> highestvals back into d? >> >> advice appreciated. >> >> sincerely, >> >> /iaw >> ---- >> Ivo Welch (ivo.we...@brown.edu, ivo.we...@gmail.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. >> > ______________________________________________ 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.
