Steve H, How much is 'much better' and 'much longer' please? And on how many rows/GB? What is the bigger picture, and why are you concatenating strings together and using paste() at all? Guess 1: you can include the x column in your key; e.g. setkey(grp,x), then there would be no need to sort(x) again. Guess 2: sorting character can be slow. Hence we don't allow character columns in keys (yet); data.table converts character to factor. But, ideally, more information at a higher level would help us to help. Matthew
On Fri, 2011-05-06 at 12:16 -0700, Steve Harman wrote: > Connected to this RMySQL performs much better > (using GROUP BY and functions such as GROUP_CONCAT which allows you > to > order and use a separator too). > > So, I would recommend using them if you want grouping with sorting. > > On May 6, 2:36 pm, Steve Harman <[email protected]> wrote: > > Hello ! > > When grouping using data.table, mean and sum functions applied within > > groups work well but if we use sort(x) function it takes much longer. > > > > I would like to do first sort(x) and put it inside paste such as > > paste(sort(x),collapse=",") > > I was wondering if there is any more efficient of effective way of > > doing this? > > > > thanks in advance, > > > > Steve > > _______________________________________________ > > datatable-help mailing list > > [email protected]https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatabl... > _______________________________________________ > 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
