yes, or as a verb 6 (4 $. $.@:=) i.4 3
2 0 On Friday, November 13, 2020, 01:04:39 p.m. EST, Ric Sherlock <[email protected]> wrote: How about 4 $. $. 6=M 1 1 On Sat, 14 Nov 2020, 06:54 Hauke Rehr, <[email protected]> wrote: > plus, Henry’s solution looks more idiomatic (too me, at least) > > usually, I try to keep related structures aligned (using grade) > other than that, I hardly remember any cases when linear indexing > didn’t do the job, maybe after some reduction > > so I think in most cases this should not be needed > but if so, I’d take Henry’s approach > > Am 13.11.20 um 18:40 schrieb 'robert therriault' via Programming: > > Having seen Henry's solution, I see that I have left the job half done, > so here is the rest of my solution. > > > > dyadind =. ;@:(= #"1 {@({@i."0 @$@])) > > 6 dyadind i. 3 4 > > 1 2 > > > > Having produced that, I note that Henry's is twice as fast and takes up > half the space and the differences become more apparent at higher > dimensions. > > > > 1000 timespacex '6 dyadind i. 3 4' > > 1.807e_6 4288 > > 1000 timespacex '6 ($@] #: I.@(= ,)) i. 3 4' > > 8.68e_7 2496 > > 1000 timespacex '6 dyadind i. 2 3 3 4' > > 5.283e_6 12992 > > 1000 timespacex '6 ($@] #: I.@(= ,)) i. 2 3 3 4' > > 1.05e_6 3008 > > > > Cheers, bob > > > >> On Nov 13, 2020, at 09:25, 'robert therriault' via Programming < > [email protected]> wrote: > >> > >> Hi Thomas, > >> > >> I usually use something like this which relies on Category ({) to group > the indices generated by i. applied to each index of the shape. I imagine > others have different approaches. > >> > >> i. 3 4 > >> 0 1 2 3 > >> 4 5 6 7 > >> 8 9 10 11 > >> ind=.{@({@i."0 @$) > >> ind i. 3 4 > >> ┌───┬───┬───┬───┐ > >> │0 0│0 1│0 2│0 3│ > >> ├───┼───┼───┼───┤ > >> │1 0│1 1│1 2│1 3│ > >> ├───┼───┼───┼───┤ > >> │2 0│2 1│2 2│2 3│ > >> └───┴───┴───┴───┘ > >> i. 2 3 4 > >> 0 1 2 3 > >> 4 5 6 7 > >> 8 9 10 11 > >> > >> 12 13 14 15 > >> 16 17 18 19 > >> 20 21 22 23 > >> ind i. 2 3 4 > >> ┌─────┬─────┬─────┬─────┐ > >> │0 0 0│0 0 1│0 0 2│0 0 3│ > >> ├─────┼─────┼─────┼─────┤ > >> │0 1 0│0 1 1│0 1 2│0 1 3│ > >> ├─────┼─────┼─────┼─────┤ > >> │0 2 0│0 2 1│0 2 2│0 2 3│ > >> └─────┴─────┴─────┴─────┘ > >> > >> ┌─────┬─────┬─────┬─────┐ > >> │1 0 0│1 0 1│1 0 2│1 0 3│ > >> ├─────┼─────┼─────┼─────┤ > >> │1 1 0│1 1 1│1 1 2│1 1 3│ > >> ├─────┼─────┼─────┼─────┤ > >> │1 2 0│1 2 1│1 2 2│1 2 3│ > >> └─────┴─────┴─────┴─────┘ > >> > >> Cheers, bob > >> > >>> On Nov 13, 2020, at 09:05, thomas.bulka via Programming < > [email protected]> wrote: > >>> > >>> Hi everyone, > >>> > >>> still learning J, I stumbled across a problem which should be easy to > solve, but somehow I have not been able to do so, yet. Say, I have defined > a matrix M: > >>> > >>> M =: 3 4 $ >: i. 12 > >>> > >>> I now want to get the row and column index of 6 in M, which is 1 2. If > M was a vector, I could easily get the index of 6 with the help of I.: > >>> > >>> I. 6 = , M > >>> > >>> Applying I. to M in its original shape, however, returns a boolean > vector which indicates in which rows 6 has been found (at least that is my > interpretation). > >>> > >>> Is it possible to apply I. to higher rank arrays in order to receive > the complete indices of the elements I'm looking for? Or should I approach > that problem in another way? > >>> > >>> Thank you very much in advance for your help! > >>> > >>> Kind regards, > >>> > >>> Thomas > >>> > >>> ---------------------------------------------------------------------- > >>> 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 > > > > -- > ---------------------- > mail written using NEO > neo-layout.org > > ---------------------------------------------------------------------- > 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
