Ok, ok, points taken. Disregard my suggestion for rank. :-) But I agree that shape is good, so this would be a proper use of the term(s):
"A 3x5 piddle is a two-dimensional piddle with shape [3,5]." David On Thu, Jan 5, 2012 at 9:01 AM, Louis Chaillet <[email protected]> wrote: > Sorry to jump in, I was reading your discussion. > > I will vote for shape. > > Order and rank have other meanings in linear mathematics > that may confuse some readers. > > Rank (or sometimes essential rank) is also used > to denote the number of independent vectors in a matrix. In a 2D pdl > (matrix) this > can never exceed the smallest dimension. That means a 2D pdl 2 rows by 3 > columns > can not have a rank higher than 2. > > As for order. Order is used as proposed here, but also in matrix > decomposition. > For example the order of a singular (i.e. non invertable) matrix is zero > no matter > how many rows and columns it has. > > Hope it helps. Louis > > > > -- > Please note my email adres has changed to [email protected] > > > Citeren Bryan Jurish <[email protected]>**: > > On 2012-01-05 14:36, David Mertens wrote: >> >>> Yes, rank. Come to think of it, though, I was thinking "rank" would be a >>> good word in place of "number of dimensions," as in a rank-two piddle, >>> rather than a two-dimensional piddle. >>> >>> The issue arises with describing data. For example, a point in three >>> dimensional space is described by a one dimensional piddle with three >>> elements. As you can see, the word "dimension" is used in two ways, one >>> to describe the extent of space, the other to describe the shape of the >>> piddle. Using the word "rank," we would say that a point in three >>> dimensional space is described by a rank-one piddle with three elements. >>> >>> A potential revised lexicon, then, would be this: >>> >>> dims -> shape >>> ndims -> rank >>> >> >> ... I find this use of "rank" confusing, since "rank" (and "order" and >> "degree") seems to me more like words for what we've been calling the >> _size_ of a given dimension (e.g. Rank_i($p) == $p->dim($i)). IIRC, the >> usual theoretical term for the number of components of a vector space >> (i.e. the "3" in "3-D space") is in fact "dimension" (e.g. Dimension($p) >> == $p->ndims), but that's pretty much in direct contradiction with the >> usual use of "dimension" in the PDL docs, where it refers to (the >> projection of) an individual component of the vector space. Compare >> http://en.wikipedia.org/wiki/**Rank_%28linear_algebra%29<http://en.wikipedia.org/wiki/Rank_%28linear_algebra%29>and >> http://en.wikipedia.org/wiki/**Dimension_%28linear_algebra%29<http://en.wikipedia.org/wiki/Dimension_%28linear_algebra%29> >> >> In order of specificity, we would talk about a... >>> 3x5 piddle, >>> rank-two piddle >>> piddle >>> >> >> I would prefer the current "2-D piddle" to "rank-two piddle", for the >> abovementioned reasons. I agree it would be nice to have a noun for >> this property, so we could assert things about "all piddles of $THINGY >> >>> = 2" instead of "all N-D piddles with N >= 2" or "all (N>=2)-D >>> >> piddles", which are both a bit kludgy. Maybe "dimension-rank" ? Or >> maybe it's possible to distinguish between "the Dimension of a piddle" >> (ndims) and "the i^th dimension of a piddle" (dim($i)) ... although >> that's cutting it pretty fine... >> >> One final, very deep annoyance that I have is with the term "thread." It >>> should be "autoloop." But that should wait until after 2.4.10 at the >>> very least. >>> >> >> I agree, "thread" is misleading. Although it doesn't bother me much >> (anymore), I would also vote to replace it with "autoloop" at some >> unspecified point in the future. >> >> marmosets, >> Bryan >> >> On Jan 5, 2012 4:48 AM, "Matthew Kenworthy" >>> <[email protected] >>> <mailto:kenworthy@strw.**leidenuniv.nl<[email protected]>>> >>> wrote: >>> >>> The "shape" proposal is an *excellent* idea - it gets my vote! >>> >>> On Thu, Jan 5, 2012 at 5:17 AM, Craig DeForest >>> <[email protected] >>> <mailto:[email protected].**edu<[email protected]>>> >>> wrote: >>> >>> Hrm. As long as we're on terminology, how do you describe a PDL >>> with dim list [3,5]? >>> >>> We've/I've been calling it a 2-D PDL with dim sizes 3 and 5 (as >>> in "dim 0 has size 3, and dim 1 has size 5"), or alternatively a >>> 3x5-PDL. Its first row would be called a 3-PDL or a 1-D PDL >>> with size 3. >>> >>> >>> My preference is "3x5 PDL" as "2d 3x5 PDL" is a bit redundant. >>> >>> I'd say no to "3-PDL" - I'd prefer "1-D PDL with size 3". >>> >>> "A PDL with shape 3 by 5" sounds good to me! >>> >> >> >> -- >> Bryan Jurish "There is *always* one more bug." >> [email protected] -Lubarsky's Law of Cybernetic Entomology >> >> >> ______________________________**_________________ >> Perldl mailing list >> [email protected] >> http://mailman.jach.hawaii.**edu/mailman/listinfo/perldl<http://mailman.jach.hawaii.edu/mailman/listinfo/perldl> >> >> > > > ______________________________**_________________ > Perldl mailing list > [email protected] > http://mailman.jach.hawaii.**edu/mailman/listinfo/perldl<http://mailman.jach.hawaii.edu/mailman/listinfo/perldl> > -- Sent via my carrier pigeon.
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