Hi, On Wed, Mar 2, 2011 at 4:22 AM, Matthew Dowle <[email protected]> wrote: > Yes, good idea. I thought the grouping columns would already be in scope > actually, that was an oversight. Intention was just to change .SD. The > first item of each group needs to be installed in scope then. If you > feel like looking: internally .SD points to itself so you can use > variables alongside .SD. It's the upper level that needs a small loop to > set them. I didn't like the .BY on first glance, but thinking about it > maybe that could be useful too in cases when you write generic code that > works when the by column names vary. You could have .BY pointing to > itself, too. .BY would contain a set of 1-length vectors. There's a FAQ > that answers why j needs grp[1] rather than grp, so that would be better > and no longer needed as grp would be length 1 anyway. Sorry I realise > that's all English and no R examples, will add later if needed.
I actually got the gist of it. I agree that .BY is a bit ugly, but I was also thinking of the "generic code" scenario you mentioned. I didn't think of just installing the by variables in scope as well so we can reference them like we do the column names of the current .SD (ie. no qualifiers/whatever needed), but that'd be quite nice, too. I'll take some time to look at the implementation details later, though I reckon I'll be chasing my tail for a while there. Thanks, -steve -- Steve Lianoglou Graduate Student: Computational Systems Biology | Memorial Sloan-Kettering Cancer Center | Weill Medical College of Cornell University Contact Info: http://cbio.mskcc.org/~lianos/contact _______________________________________________ datatable-help mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
