Is this what you want?
a=:i.4 4
m=:1 1 0 0,:0 1 1 1
(8$m)*(2#a)
0 1 0 0
0 1 2 3
4 5 0 0
0 5 6 7
8 9 0 0
0 9 10 11
12 13 0 0
0 13 14 15
On Thu, Sep 6, 2012 at 8:28 AM, Devon McCormick <devon...@gmail.com> wrote:
> I'm not as conversant with rank as you are. To my way of thinking,
> you want to multiply each row of "a" by each row of the multiplier:
>
> a *"1/2 4$ 1 1 0 0 0 0 1 1
> 1 1 0 0
> 0 0 1 1
>
> 1 1 0 0
> 0 0 2 2
>
> 1 1 0 0
> 0 0 3 3
>
> 1 1 0 0
> 0 0 4 4
>
> This gives a 3-D result, which may be handy depending on what you next
> plan to do with this. However, as David shows, you can also ravel the
> first two dimensions into one:
>
> ,/a *"1/2 4$ 1 1 0 0 0 0 1 1
> 1 1 0 0
> 0 0 1 1
> 1 1 0 0
> 0 0 2 2
> 1 1 0 0
> 0 0 3 3
> 1 1 0 0
> 0 0 4 4
>
>
> On Wed, Sep 5, 2012 at 9:56 PM, David Ward Lambert
> <b49p23t...@stny.rr.com> wrote:
> > Right! "Matrix multiplication" usually means something else.
> > You want a sort of element-by-corresponding-element multiplication.
> >
> > B ; A
> > +-------+-------+
> > |1 1 0 0|1 1 1 1|
> > |0 0 1 1|1 1 2 2|
> > | |1 1 3 3|
> > | |1 1 4 4|
> > +-------+-------+
> >
> > A solution uses rank conjunction twice. I couldn't begin to understand
> > it the first time I saw this sort of construction. Then one day I wrote
> > rank rank and retrospectively realized what I'd written and understood.
> > I practiced rank with sentences like 'abc' "2 i. 2 3 4
> >
> > My thoughts to construct this sentence:
> > First I realized that you need to multiply row by row.
> > The ("1) adverb ensures this. The frames of these two matrices disagree
> > because there are 2 rows in B and 4 in A. The next adverb ("_ 1) means
> > (because ultimately the final verb is dyadic) "use all of the left array
> > with each row of the right hand array".
> >
> > B * ("1) ("_ 1) A
> > 1 1 0 0
> > 0 0 1 1
> >
> > 1 1 0 0
> > 0 0 2 2
> >
> > 1 1 0 0
> > 0 0 3 3
> >
> > 1 1 0 0
> > 0 0 4 4
> >
> > Finally, inserting append between the pages gives
> >
> > ,/B*"1"_ 1 A
> > 1 1 0 0
> > 0 0 1 1
> > 1 1 0 0
> > 0 0 2 2
> > 1 1 0 0
> > 0 0 3 3
> > 1 1 0 0
> > 0 0 4 4
> >
> >
> > ----------------------------------------------------------------------
> > For information about J forums see http://www.jsoftware.com/forums.htm
>
>
>
> --
> Devon McCormick, CFA
> ^me^ at acm.
> org is my
> preferred e-mail
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
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