Hi, On Thu, Jul 21, 2011 at 3:27 AM, Emmanuel Blondel <[email protected]> wrote: > Dear all, > > I have a datatable (mydt) with a reference column (code) for which I set a > key, and a set of numeric columns (A ,B, C, D, E). > I obtain this from a serie of script codes, but the issue is that I have > duplicated rows (code), So i want to do is according to codestation, for > each of the columns.. > > I could do the following code for one single column: > result<-mydt[,sum(A),by=code] > > but I would like to know if it is possible to do it for each of the columns, > so I get a databable with the same columns with sum value, group by > codestation. Do you have any suggestion?
Do you mean something like: R> mydt[, list(A=sum(A), B=sum(B), C=sum(C), D=sum(D), E=sum(E)), by=code] or equivalently, but maybe slower (there is a recent thread on the list about this): R> mydt[, lapply(.SD, sum), by=code] Is that what you are after? -steve -- Steve Lianoglou Graduate Student: Computational Systems Biology | Memorial Sloan-Kettering Cancer Center | Weill Medical College of Cornell University Contact Info: http://cbio.mskcc.org/~lianos/contact _______________________________________________ datatable-help mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
