Thanks David for your suggestions. On Thu, Dec 3, 2009 at 2:03 PM, David Winsemius <dwinsem...@comcast.net>wrote:
> > On 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. >> > > ?tapply > > as in > > sum.tbl <- with(dftbl, tapply(Value, list(State, Month), sum) ) > > > Also, I may need to calculate mean value along with "sum". >> > > Use the mean function in the above formulation to get means, length to get > counts, or perhaps summary .... or one of the several packages that offer a > "describe" function. So many functions, so little time. > > -- David > > > >> 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<http://www.r-project.org/posting-guide.html> >> and provide commented, minimal, self-contained, reproducible code. >> > > David Winsemius, MD > Heritage Laboratories > West Hartford, CT > > [[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.
