On 5/23/07, Gabor Grothendieck <[EMAIL PROTECTED]> wrote: > On 5/23/07, Martin Maechler <[EMAIL PROTECTED]> wrote: > > >>>>> "GaGr" == Gabor Grothendieck <[EMAIL PROTECTED]> > > >>>>> on Wed, 23 May 2007 08:56:50 -0400 writes: > > > > GaGr> On 5/23/07, Seth Falcon <[EMAIL PROTECTED]> wrote: > > >> Andrew Clausen <[EMAIL PROTECTED]> writes: > > >> > > >> > Hi Seth, > > >> > > > >> > On Mon, May 21, 2007 at 05:15:10PM -0700, Seth Falcon wrote: > > >> >> I will also add that the notion of a default argument on a generic > > >> >> function seems a bit odd to me. If an argument is available for > > >> >> dispatch, I just don't see what sense it makes to have a default. > > In > > >> >> those cases, the default should be handled by the method that has a > > >> >> signature with said argument matching the "missing" class. > > >> >> > > >> >> What often does make sense is to define a generic function where > > some > > >> >> argument are not available for dispatch. For example: > > >> >> > > >> >> setGeneric("foo", signature="flesh", > > >> >> function(flesh, skeleton=attr(flesh, "skeleton") > > >> >> standardGeneric("foo"))) > > >> > > > >> > That's an excellent suggestion. Thanks! However, I had to set the > > signature > > >> > to c("numeric", "missing") rather than just "numeric". > > >> > > > >> > I have uploaded a new version here: > > >> > > > >> > http://www.econ.upenn.edu/~clausen/computing/relist.R > > >> > > >> I misunderstood. You aren't using S4 classes/methods at all > > >> and so I don't actually see how my comments could have been helpful in > > >> any way. relist seems like a really odd solution to me, but based on > > >> the discussion I guess it has its use cases. > > > > GaGr> You didn't misunderstand but there was an offline > > GaGr> discussion pointing out that one primary use is in the > > GaGr> inner loop of an optimization so it should be made as > > GaGr> efficient as possible and it was changed with that in > > GaGr> mind. > > > > Thank you Gabor for that explanation. > > (I had wondered, too, and was glad that Andrew had dropped S4 > > generics seemingly "by himself" ;-)) > > > > Re your proposal of mixing this into reshape(): > > > > I think it's a nice and didactly helpful idea to point out the > > similarity in concepts between reshape() and relist(). > > > > However, I wouldn't like to make reshape() generic in this > > sense: As Andrew has mentioned as well, I think the two topics > > of data.frame (/matrix) reshaping and list <-> vector transformation > > seem too much different... > > > > Martin > > > > Another possibility is to call it reshapeList instead of relist or reshape and > the argument list made similar to reshape to keep the analogy as to > reshape as close as possible to leverage the R user's knowledge of > reshape. > > However, I am not so sure it really is different. Both reshape and > relist involve flattening of structures and then reconstructing them back > to the original. This seems very similar to me.
The cast and melt operators in reshape are already generic, if you wanted to hook onto those instead. Hadley ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel