Nice thing about R is there are a number of ways to do things: > x identifier quantity 1 1 10 2 1 20 3 2 30 4 1 15 5 2 10 6 3 20 > require(sqldf) > sqldf('select identifier, sum(quantity) as quantity from x group by > identifier') identifier quantity 1 1 45 2 2 40 3 3 20 >
or using 'data.table' > require(data.table) Loading required package: data.table > x <- data.table(x) > x[, sum(quantity), by = identifier] identifier V1 [1,] 1 45 [2,] 2 40 [3,] 3 20 On Thu, Dec 2, 2010 at 11:24 AM, chris99 <chea...@hotmail.com> wrote: > > I am trying to aggregate data in column 2 to identifiers in col 1 > > eg.. > > take this> > > identifier quantity > 1 10 > 1 20 > 2 30 > 1 15 > 2 10 > 3 20 > > and make this> > > identifier quantity > 1 45 > 2 40 > 3 20 > > > Thanks in advance for your help! > -- > View this message in context: > http://r.789695.n4.nabble.com/Help-summarizing-R-data-frame-tp3069624p3069624.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. > -- Jim Holtman Data Munger Guru What is the problem that you are trying to solve? ______________________________________________ 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.