see package plyr, especially the function ddply(), eg.., in your case: ddply(dataframe, .(columnA, columnB), summarise, columnC = length(columnB) )
Scott On Wednesday, March 2, 2011 at 9:10 AM, Simone Gabbriellini wrote: > Hello List, > > I would like to simplify a data.frame like this > > columnA columnB > user10 proj12 > user10 proj19 > user10 proj12 > > into something like: > > columnA columnB columnC > user10 proj12 2 > user10 proj19 1 > > I know unique() can simplify the data.frame, but how to count and store the > duplicates? > > thanks in advance for any help. > > best regards, > Simone > > ______________________________________________ > 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. > [[alternative HTML version deleted]] ______________________________________________ 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.
