I would agree that a empty data table is the expected result I would have had. If I do
DT[, sum(v), by=x] I always expect a two column data.table with columns "x" and "V1" (which is sum(x)). In SQL this would read SELECT x, SUM(v) FROM DT GROUP BY x So with DT[y<1, sum(v), by=x] we have SELECT x, SUM(v) FROM DT WHERE y < 1 GROUP BY x Now in any SQL dialect I work with, if WHERE y < 1 didn't return any rows, then the result of this would be a 0 row selection. I believe that is what it should be with data.table as well: a 0-row data.table with columns "x" and "V1". This is a valid bug IMO, and should definitely be fixed. On Wed, Apr 18, 2012 at 3:32 AM, Matthew Dowle <[email protected]> wrote: > Dear datatablers, > > This seems like a valid bug report. Any reasons why we shouldn't make > this change? > > https://r-forge.r-project.org/tracker/?func=detail&atid=975&aid=1945&group_id=240 > > Matthew > > > > _______________________________________________ > 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
