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 and 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:[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]>> 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
