Thanks Bob Nice call. I might start using that, even if only for comparison. I'll be the first to admit that I haven't been on the friendliest of terms with the std Vocabulary. Well, alright... but only sometimes.
On 23 April 2014 18:58, robert therriault <bobtherria...@mac.com> wrote: > Hey Alex, > > You may want to take a look at NuVoc, the jwiki section that I think that > Ian Clark organized just for the reason that you are describing. :) > > http://www.jsoftware.com/jwiki/NuVoc > > Cheers, bob > > > On Apr 23, 2014, at 10:52 AM, alexgian <alexg...@blueyonder.co.uk> wrote: > > >> The information and more are in the vocabulary page for %. > > > > Well, yes, but so tersely and compactly expressed that you have to know > the > > long answer before you understand it! I did look at the Vocab page, but > > didn't "get it", that's why I posted. > > > > It needed Roger's somewhat more expanded explanation for those of us that > > are somewhat slower on the uptake. That's why I said the Vocab could > use a > > touch up. It is NOT user friendly, more of an ultra-coded reference. Of > > course, you might not see it this way, but I'd bet most newcomers would. > > > > And it's not as if there is a longer explanation somewhere else, is > there? > > Well, other than this thread, I mean... :) > > > > > > > > On 23 April 2014 18:17, Roger Hui <rogerhui.can...@gmail.com> wrote: > > > >> The information and more are in the vocabulary page for %. > >> http://www.jsoftware.com/help/dictionary/d131.htm . > >> > >> > >> On Wed, Apr 23, 2014 at 10:02 AM, alexgian <alexg...@blueyonder.co.uk > >>> wrote: > >> > >>> Great info, thanks Roger. > >>> If it was up to me, I'd DEFINITELY include that in the Vocabulary, is > it > >>> even documented anywhere else? > >>> > >>> > >>> On 23 April 2014 17:33, Roger Hui <rogerhui.can...@gmail.com> wrote: > >>> > >>>> %. x for a vector x is the same as ($x)$%.,.x, and the key expression > >> is > >>>> %.,.x, the "matrix inverse" of a 1-column matrix. b=.y%.x on a tall > >>> matrix > >>>> x is solving a least-squares problem, the coefficients b that > minimizes > >>> the > >>>> sum of squares of y - x +/ .* b . > >>>> > >>>> In addition, for a non-zero vector x, (%.x) +/ .* x is 1, a special > >> case > >>> of > >>>> that (%.x)+/ .* x is an identity matrix, whence one can deduce that > for > >>>> vector x, %.x is x%+/x^2. > >>>> > >>>> ] x=: 7 ?.@$ 100 > >>>> 94 56 8 6 85 48 66 > >>>> %. x > >>>> 0.00362137 0.00215741 0.000308202 0.000231152 0.00327465 0.00184921 > >>>> 0.00254267 > >>>> (%.x) +/ .* x > >>>> 1 > >>>> x % +/x^2 > >>>> 0.00362137 0.00215741 0.000308202 0.000231152 0.00327465 0.00184921 > >>>> 0.00254267 > >>>> > >>>> M=: 7 3 ?.@$ 100 > >>>> (%.M) +/ .* M > >>>> 1 5.55112e_17 _2.77556e_17 > >>>> _1.21431e_16 1 1.11022e_16 > >>>> _4.85723e_17 1.94289e_16 1 > >>>> > >>>> > >>>> > >>>> On Wed, Apr 23, 2014 at 9:13 AM, alexgian <alexg...@blueyonder.co.uk> > >>>> wrote: > >>>> > >>>>> Just wondering: > >>>>> %. 2 3 4 > >>>>> 0.0689655 0.103448 0.137931 > >>>>> > >>>>> Which is fair enough enough at one level, I suppose, since the dot > >>>> product > >>>>> of the two arrays IS 1, but what system/equation is being solved > >> here? > >>>>> Obviously, there are infinite solutions. Why that one? > >>>>> IOW, which "matrix" is being inverted here? > >>>>> > >>>>> Thanks > >>>>> > >> ---------------------------------------------------------------------- > >>>>> For information about J forums see > >> http://www.jsoftware.com/forums.htm > >>>>> > >>>> ---------------------------------------------------------------------- > >>>> For information about J forums see > http://www.jsoftware.com/forums.htm > >>>> > >>> ---------------------------------------------------------------------- > >>> For information about J forums see http://www.jsoftware.com/forums.htm > >>> > >> ---------------------------------------------------------------------- > >> For information about J forums see http://www.jsoftware.com/forums.htm > >> > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
