Perhaps
,"1/,"2/,"3/>zz
Thanks,
--
Raul
On Thu, Nov 20, 2014 at 10:42 AM, Ben Gorte - CITG
<b.g.h.go...@tudelft.nl> wrote:
> If I'm allowed to jump in here, I'm using ;. a lot to subdivide images into
> 2x2 blocks (think wavelet), and I guess it's okay to do it like:
>
> ]z =: (2 2,:2 2) < ;. _3 i.4 6
> +-----+-----+-----+
> |0 1 |2 3 | 4 5|
> |6 7 |8 9 |10 11|
> +-----+-----+-----+
> |12 13|14 15|16 17|
> |18 19|20 21|22 23|
> +-----+-----+-----+
>
> I was quite happy to discover that:
>
> ,./,./> z
> 0 1 2 3 4 5
> 6 7 8 9 10 11
> 12 13 14 15 16 17
> 18 19 20 21 22 23
>
> does the inverse (it's even pleasant to type).
>
> Now I'm smoothly moving to 3d with
>
> ]zz =: (2 2 2,:2 2 2) < ;. _3 i.4 6 8
>
> but as the inverse is concerned I'm sort of stuck at:
>
> CutBack =: [: ([: ,/ ([: ,./ ,./)"4) 1 2 4 5&|:
> (i.4 6 8) -: CutBack >zz
> 1
>
> which I'm sure can be improved. Any suggestions?
>
> Thanks,
> Ben
> ________________________
> From: programming-boun...@forums.jsoftware.com
> [programming-boun...@forums.jsoftware.com] on behalf of Henry Rich
> [henryhr...@nc.rr.com]
> Sent: Wednesday, November 19, 2014 23:40
> To: programm...@jsoftware.com
> Subject: Re: [Jprogramming] Boxing columns
>
> Is the inverse implemented using ^:_1 ? I couldn't find it.
>
> I come up with ,.&:>/ as an inverse for ('';1)&(<;.1) .
>
> Henry Rich
>
> On 11/19/2014 5:28 PM, Roger Hui wrote:
>> The inverse of this "block matrices cut" is also interesting.
>>
>>
>> On Wed, Nov 19, 2014 at 2:27 PM, Roger Hui <rogerhui.can...@gmail.com>
>> wrote:
>>
>>> ('';1) <;.1 i.3 3
>>> ┌─┬─┬─┐
>>> │0│1│2│
>>> │3│4│5│
>>> │6│7│8│
>>> └─┴─┴─┘
>>>
>>>
>>> On Wed, Nov 19, 2014 at 2:05 PM, Henry Rich <henryhr...@nc.rr.com> wrote:
>>>
>>>> boxcols i. 3 3
>>>> +-+-+-+
>>>> |0|1|2|
>>>> |3|4|5|
>>>> |6|7|8|
>>>> +-+-+-+
>>>>
>>>> Can you write boxcols?
>>>>
>>>> Can you write it tacitly without using a hook, fork, compose, or appose?
>>>>
>>>> Henry Rich
>>>> ----------------------------------------------------------------------
>>>> For information about J forums see http://www.jsoftware.com/forums.htm
>>>>
>>>
>>>
>> ----------------------------------------------------------------------
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>>
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