Or:
f
3 3 +/@:((0) 4} ,);._3 ([: |: {: , ] , {.)^:2
f 1+i.3 3
44 43 42
41 40 39
38 37 36
Linda
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Aai
Sent: Tuesday, November 13, 2012 8:17 AM
To: [email protected]
Subject: Re: [Jprogramming] Matrix Transformations based on local
submatrices
Hmmm, no need for selecting, so:
3 3 +/@:((0) 4},);._3 |:@({:,],{.)^:(2)1+i.3 3
On 13-11-12 14:13, Aai wrote:
> Just a possibility for the interesting case of a torus:
>
> 3 3 +/@:(#~0<])@((0) 4},);._3 |:@({:,],{.)^:(2)1+i.3 3
> 44 43 42
> 41 40 39
> 38 37 36
>
>
> torus elements flattened:
>
> |:@({:,],{.)^:(2)1+i.3 3
>
> and then using
> 3 3 f ;. _3
>
> with f selecting and summing
>
>
>
> On 13-11-12 12:43, Alex Giannakopoulos wrote:
>> OK, I'm trying to do some work with matrices that involves
>> transformations based on local properties of a matrix (neighbouring
>> elements).
>> This is the sort of thing you may find in image-processing
>> "edge-detection", etc, or in some cellular automata of the type of
>> Conway's "Life".
>>
>> In other words, I want to be able to supply a matrix, and have it so
>> processed that the result is a new matrix where each new element was
>> determined by a function which processed the old elements neighbours.
>>
>> Any direction, relevant help pages, etc, much appreciated.
>> If anyone would go as far as offering some sample code that would be
>> great, too!
>> As a trivial example, suppose I want to calculate the sum of the
>> neighbours of each element Say we have a matrix m0 =. 3 3 $ >:i.9
>> What I want is the verb "neighbours" whereby
>> neighbours m0
>> 11 19 13
>> 23 40 27
>> 17 31 19
>>
>> Obviously, I am maily interested in how to extract the "neighbours"
>> submatrix, without resorting to explicit looping, if that is possible.
>> To make it a bit more interesting, how would I extract the neighbours
>> if the matrix was a torus or infinite tiling, such that:
>> neighb-torus m0
>> 44 43 42
>> 41 40 39
>> 38 37 36
>>
>> Thanks for any suggestions!
>> Alex
>> ---------------------------------------------------------------------
>> - For information about J forums see
>> http://www.jsoftware.com/forums.htm
>
--
Met vriendelijke groet,
@@i = Arie Groeneveld
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