as.data.table(lapply(DT, sum)) works and doesn't seem much less elegant? (Well -- it would work if you were not trying to take the sum of a factor ;-))
t On Mon, Jan 9, 2012 at 4:45 PM, Joseph Voelkel <[email protected]> wrote: > # from help(data.table)**** > > DT = data.table(x=rep(c("a","b","c"),each=3), y=c(1,3,6), v=1:9)**** > > DT[,lapply(.SD,sum),by=x] # this works fine**** > > ** ** > > # but this fails**** > > DT[,lapply(.SD,sum)]**** > > # with this message: Error in lapply(.SD, sum) : object '.SD' not found*** > * > > ** ** > > # Am I missing something obvious here?**** > > ** ** > > _______________________________________________ > datatable-help mailing list > [email protected] > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help >
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