well numeric(0) is no data, but because in the first case there was other data to output and you also asked to output `y`, what else was it supposed to do? ( it might help to look at the output of c(numeric(0), numeric(0)) )
On Fri, May 17, 2013 at 3:38 PM, Gabor Grothendieck <[email protected] > wrote: > In the first case it replaced the zero length component with NA and in > the second case it did not. Why the difference? > > On Fri, May 17, 2013 at 4:33 PM, Eduard Antonyan > <[email protected]> wrote: > > Maybe I'm missing smth, but what else did you expect? Looks like it did > it's > > best to compensate for the user not supplying full data in the first > > example, and there really was nothing to do in the second one. > > > > > > > > On Fri, May 17, 2013 at 3:27 PM, Gabor Grothendieck > > <[email protected]> wrote: > >> > >> Is this intended? If we use j = list(x = "X", y = numeric(0)) we get > >> a row but if we use just list(y = numeric(0)) then we do not get a > >> row. In the first case it filled in the zero length component with NA > >> and in the second case it just omitted the row entirely: > >> > >> > dd <- data.table(a = 1:3) > >> > dd > >> a > >> 1: 1 > >> 2: 2 > >> 3: 3 > >> > dd[, list(x = "X", y = numeric(0)), by = a] > >> a x y > >> 1: 1 X NA > >> 2: 2 X NA > >> 3: 3 X NA > >> > dd[, list(y = numeric(0)), by = a] > >> Empty data.table (0 rows) of 2 cols: a,y > >> > >> > >> -- > >> Statistics & Software Consulting > >> GKX Group, GKX Associates Inc. > >> tel: 1-877-GKX-GROUP > >> email: ggrothendieck at gmail.com > >> _______________________________________________ > >> datatable-help mailing list > >> [email protected] > >> > >> > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help > > > > > > > > -- > Statistics & Software Consulting > GKX Group, GKX Associates Inc. > tel: 1-877-GKX-GROUP > email: ggrothendieck at gmail.com >
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