>>>>> Gabriel Becker
>>>>> on Fri, 17 May 2019 01:06:11 -0700 writes:
> Hi Martin,
> Thanks for chiming in. Responses inline.
> On Fri, May 17, 2019 at 12:32 AM Martin Maechler
<maech...@stat.math.ethz.ch>
> wrote:
>> >>>>> Gabriel Becker
>> >>>>> on Thu, 16 May 2019 15:47:57 -0700 writes:
>>
>> > Hi Hadley,
>> > Thanks for the counterpoint. Response below.
>>
>> > On Thu, May 16, 2019 at 1:59 PM Hadley Wickham <h.wick...@gmail.com>
>> wrote:
>>
>> >> The existing behaviour seems inutitive to me. I would consider these
>> >> invariants for n vector x_i's each with size m:
>> >>
>> >> * nrow(rbind(x_1, x_2, ..., x_n)) equals n
>> >>
>>
>> > Personally, no I wouldn't. I would consider m==0 a degenerate case,
>> where
>> > there is no data, but I personally find matrices (or data.frames)
>> with rows
>> > but no columns a very strange concept. The converse is not true, I
>> > understand the utility of columns but no rows, particularly in the
>> > data.frame case, but rows with no columns are observations we didn't
>> > observe anything about. Strange, imho.
>>
>> Gabe, here I have to very strongly disagree.
>>
>> Matrices (and higher order Arrays) are always definitely to
>> behave "symmetrically" / "uniformly" with respect to all of their
>> dimensions.
>>
>> We (and the S developers before us) have always taken a lot of
>> care trying to ensure that this is true.
>>
>> So for the matrix case, if rows and columns behaved differently
>> that would be a bug "by definition".
>>
> I realize now I could have been clearer/more explicit about this, but I
> wasn't arguing that the behavior should be different between columns and
> rows, just that the behavior in the rows case didn't necessarily make a
ton
> of sense to me. I was arguing that a change to both rbind and cbind be
> considered when all length zero vectors are passed, not that rbind change
> without cbind also changing. I will admit even here to feeling much more
> strongly about the data.frame case.
> That said, I do see that the cbind/columns argument seems harder (though
> not impossible) for me to make. And maybe that's a good enough reason not
> to consider such a change, because as I say, I agree the symmetry is
> important, and would (also) want cbind to change the same way rbind did
if
> such a change happened, and that might bother many? more people than the
> rbind case would. Maybe not though, based on the other responses in the
> thread.
> Honestly, the most intuitive thing for me if you rbind or cbind a bunch
of
> length zero vectors together would be a 0x0 matrix, at the very least in
> the non-named arguments case. Its a matrix with 0 elements in it, after
> all. It seems perhaps that my intuition is just somewhat non-standard
> though.
I think your "problem" may be that you've not appreciated yet
the importance of {0 x p} and {n x 0} matrices and would
think all of these should be {0 x 0} ?
Believe me we did quite a bit of reasoning and looking at
associative law and transitiveness etc at the time, which I can't easily
recall, but believe me that it has been very beneficial to
consistently deal with n x 0 and 0 x d matrices :
Much of R code could be simplified / automagically worked
correctly in edge cases, once such matrices were fulfilling
basic consistency identities.
Martin
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