many thanks, this is really a great solution! best, Simone
Il giorno 02/mar/2011, alle ore 16.22, Scott Chamberlain ha scritto: > 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. > ______________________________________________ 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.