Very good. I had: ,/,./"3 a*/b
----- Original Message ----- From: Viktor Cerovski <[email protected]> Date: Friday, February 26, 2010 8:20 Subject: Re: [Jprogramming] Kronecker Product To: [email protected] > > > Roger Hui wrote: > > > > In my opinion ,/"2,/ a */"1"1 2 b is far from straightforward; > > a*&.>< b and then "removing the boxes" is more straightforward. > > > > Another way to look at it is to note that a*/b already does the > product up to the gluing together block matrices of the result > (which > is also what (a *&$ b) ($,) 0 2 1 3 |: a */ b does), so the > product > can be written also as: > > ,./^:2 a*/b > > > > > http://www.jsoftware.com/jwiki/Essays/Kronecker_Product > > > Example from the essay: > > ] A=: 10+i.2 3 > 10 11 12 > 13 14 15 > ] B=: i.3 4 > 0 1 2 3 > 4 5 6 7 > 8 9 10 11 > A *&.> < B > +---------------+---------------+---------------+ > | 0 10 20 30 | 0 11 22 33 | > 0 12 24 36 | > |40 50 60 70 |44 55 66 77 > |48 60 72 84 | > |80 90 100 110 |88 99 110 121 |96 108 120 132 | > +---------------+---------------+---------------+ > | 0 13 26 39| 0 14 > 28 42| 0 15 30 45| > | 52 65 78 91| 56 70 84 98| > 60 75 90 105| > |104 117 130 143|112 126 140 154|120 135 150 165| > +---------------+---------------+---------------+ > ,./^:2 A */ B > 0 10 20 30 0 11 > 22 33 0 12 24 36 > 40 50 60 70 44 55 > 66 77 48 60 72 84 > 80 90 100 110 88 99 110 121 96 108 > 120 132 > 0 13 26 39 0 14 > 28 42 0 15 30 45 > 52 65 78 91 56 70 > 84 98 60 75 90 105 > 104 117 130 143 112 126 140 154 120 135 150 165 > > ----- Original Message ----- > From: Zsbán Ambrus <[email protected]> > Date: Friday, February 26, 2010 4:00 > Subject: Re: [Jprogramming] Kronecker Product > To: Programming forum <[email protected]> > > > On Fri, Feb 26, 2010 at 12:28 AM, Roger Hui > <[email protected]> > > wrote:> (a *&$ b) ($,) 0 2 1 3 |: a */ b > > > > That might be more efficient, but I think the most > > straightforward way > > to compute this is just this: > > > > ,/"2,/ a */"1"1 2 b ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
