On Tue, Mar 22, 2011 at 11:42 AM, ivo welch <ivo...@gmail.com> wrote: > 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)) > 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?
The easiest approach is probably to use ave() instead of by(). Otherwise match() will tell you where to put each number. -thomas -- Thomas Lumley Professor of Biostatistics University of Auckland ______________________________________________ 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.
