Oh, yes... I guess the vectors were not representing the indices into
the dimensions, so:
((m{~{.),.n{~{:)|:($ #: I.@,) map
aA
aD
bB
bC
(But I would probably use intermediates other than m and n, since m
and n are conjunction arguments.)
Thanks,
--
Raul
On Tue, Sep 21, 2021 at 6:46 AM 'Mike Day' via Programming
<[email protected]> wrote:
>
> Similar approach, essentially, to Ric’s, using a table of indices of the
> ones:
>
> ix =: $#:I.@,
> ix map
> 0 0
> 0 3
> 1 1
> 1 2
> ({&m@:{."1)ix map
> aabb
> ({&m@:{."1,. {&n@:{:"1)ix map
> aA
> aD
> bB
> bC
>
> Somehow, though, I think you’re after something more elegant.
>
> Sorry, the display is probably poor as typing from iPad.
>
> Cheers,
>
> Mike
>
> Sent from my iPad
>
> > On 21 Sep 2021, at 10:53, Ric Sherlock <[email protected]> wrote:
> >
> > Some variation on this?
> >
> > |:(m,:n) {~"1 |: 4$.$. map
> > aA
> > aD
> > bB
> > bC
> >
> >
> >
> >
> >> On Tue, 21 Sep 2021, 21:37 bill lam, <[email protected]> wrote:
> >>
> >> Say I have a boolean matrix
> >> ] map=. 3 4 $ 1 0 0 1 0 1 1 0 0 0 0 0
> >> 1 0 0 1
> >> 0 1 1 0
> >> 0 0 0 0
> >>
> >> and 2 vectors of dimension equal to the 2 sides of the matrix
> >> m=. 'abc' [ n=. 'ABCD'
> >> I want a cross product for those 1 in the matrix, with result like this
> >> _2 ]\ 'aAaDbBbC'
> >> aA
> >> aD
> >> bB
> >> bC
> >>
> >> Is it possible to do it without explicit loops? The dimension of the matrix
> >> can be very large so that generating all cross products then eliminating is
> >> not an option.
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