Here's a related expression.

   4 4 4 4 #."1 0 i. 4
0 85 170 255

I like how this relates array structure to polynomial structure.

-- 
Raul

On Wed, Mar 6, 2013 at 9:22 AM, Linda Alvord <[email protected]> wrote:
> I like:
>
>    (<0 1 2 3)|:B=:i.4 4 4 4
> 0 85 170 255
>
> Linda
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Don Guinn
> Sent: Wednesday, March 06, 2013 8:19 AM
> To: [email protected]
> Subject: Re: [Jprogramming] extacting the main diagonal of a square matrix
>
>    (<0 1 2)|:B
> 0 13 26
>
> Or -
>    (<i.#$B)|:B=.i. 3 3 3 3
> 0 40 80
>
> On Wed, Mar 6, 2013 at 12:35 AM, Linda Alvord
> <[email protected]>wrote:
>
>> Don, my function doesn't apply to a 3D array. However, shouldn't the
>> diagonal of  B  be  0 13 26 ?
>>
>>    ]B=:i.3 3 3
>>  0  1  2
>>  3  4  5
>>  6  7  8
>>
>>  9 10 11
>> 12 13 14
>> 15 16 17
>>
>> 18 19 20
>> 21 22 23
>> 24 25 26
>>
>>    (<0 1)|:B
>> 0 12 24
>> 1 13 25
>> 2 14 26
>>
>> Linda
>> -
>>
>>
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