Hi Peng, Here is a suggestion using tapply:
R> with(x, tapply(Value, list(State, Month), FUN = sum)) R> with(x, tapply(Value, list(State, Year), FUN = sum)) R> with(x, tapply(Value, list(State, Year, Month), FUN = sum)) with 'x' your data set. Please take a look at ?tapply for more information. Another useful functions might be ?ave and ?aggregate. Best, Jorge On Thu, Dec 3, 2009 at 1:50 PM, Peng Cai <> wrote: > Hi R Users, > > I'm wondering how can I calculate two (or three) way sum of a variable. A > sample data is: > > State Month Year Value > NC Jan 1996 1 > NC Jan 1996 2 > NC Feb 1997 2 > NC Feb 1997 3 > NC Mar 1998 3 > NC Mar 1998 4 > NY Jan 1996 4 > NY Jan 1996 5 > NY Feb 1997 5 > NY Feb 1997 6 > NY Mar 1998 6 > NY Mar 1998 7 > > I'm trying to sum up "value" column by State*Month and by State*Month*Year. > Also, I may need to calculate mean value along with "sum". > > Any help would be greatly appreciated, > > Thanks, > Peng > > [[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. > [[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.
