Thanks. .N and .BY added to FR#1732. On Tue, 2012-01-10 at 17:28 -0500, Joseph Voelkel wrote: > Same issue with .N and .BY, not surprisingly. > > Regarding > "as.data.table(lapply(DT, sum)) works and doesn't seem much less elegant?" > > In my example, I was writing several statements of .SD with by=, and then > wanted a statement > Without the by=. It just seemed that I shouldn't need to change .SD to DT ... > Same fundamental point as Chris's but not is as elegant a context. > > > -----Original Message----- > From: Matthew Dowle [mailto:[email protected]] On Behalf Of > Matthew Dowle > Sent: Monday, January 09, 2012 5:15 PM > To: Chris Neff > Cc: [email protected]; Joseph Voelkel; > [email protected] > Subject: Re: [datatable-help] .SD without by seems to fail > > Ok, very persuasive. I've raised a bug report : > > https://r-forge.r-project.org/tracker/index.php?func=detail&aid=1732&group_id=240&atid=975 > > > On Mon, 2012-01-09 at 14:01 -0500, Chris Neff wrote: > > I think the original example should be able to work. There are times > > where I am dynamically building the by list based on the number of > > subslice keys I have for my data.table. Sometimes I have to aggregate > > over a certain key, so if my keys are "x" and "y" and I have value > > columns V1, V2, V3 I will do something like: > > > > by.cols = setdiff(key(DT), "x") > > DT[, sum(V1), by=by.cols] > > > > Now if I only have one key column "x", I want this to aggregate over > > the whole data.table. This in the past didn't work until I submitted a > > bug report and it was fixed, but I never have had to do it with the > > whole .SD. But I could easily see wanting to do > > > > DT[, lapply(.SD, sum), by=by.cols] > > > > especially if I include .SDcols with it too. And I don't want to have > > to check for an empty by.cols and do some different code just for that > > case. It makes sense to have it all consistent. > > > > > > 2012/1/9 Timothée Carayol <[email protected]>: > > > 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 > > > > > > > > > > > > _______________________________________________ > > > datatable-help mailing list > > > [email protected] > > > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help > > _______________________________________________ > > datatable-help mailing list > > [email protected] > > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help > >
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