?tapply e.g.
with(yourdata, tapply(A,list(year,month),sum,simplify=FALSE)) This assumes "sum them up" means summing each column separately. You were unclear as to exactly what you meant by this. -- Bert Bert Gunter Genentech Nonclinical Biostatistics (650) 467-7374 "Data is not information. Information is not knowledge. And knowledge is certainly not wisdom." Clifford Stoll On Mon, Sep 8, 2014 at 12:08 PM, eliza botto <eliza_bo...@hotmail.com> wrote: > Dear R members, > > I have this data frame of 100 years in the following format > > year month day A B C D > > where A,B,C and D are item number sold each day. I am trying > > 1-split the data w.r.t the monthly values for each year > > 2-then, sum them up > > I am pasting here just a part of data to make it more clearer > > structure(list(year = c(1961, 1961, 1961, 1961, 1961, 1961, 1961, > 1961, 1961, 1961, 1961, 1961), month = c(1, 1, 1, 1, 1, 1, 1, > 1, 1, 1, 1, 1), day = 1:12, A = 1:12, B = 3:14, C = 6:17, D = 16:27), .Names > = c("year", > "month", "day", "A", "B", "C", "D"), row.names = c(NA, 12L), class = > "data.frame") > > I initially tried to use "dcast" command but for no use. > > Your kind help is needed. > > Thanks in advance > > Eliza > > > > [[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. ______________________________________________ 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.