Hi Jon,
It's ugly, as in 'I can make this fit with a hammer' ugly, but this works
3 4 ((({.@[){.]) , ({:@[){.])"1 arr
0 1 2 0 1 2 3
6 7 8 6 7 8 9
2 3 4 2 3 4 5
8 9 0 8 9 0 1
4 5 6 4 5 6 7
0 1 2 0 1 2 3
6 7 8 6 7 8 9
2 3 4 2 3 4 5
8 9 0 8 9 0 1
4 5 6 4 5 6 7
Cheers, bob
On Sep 26, 2014, at 10:22 AM, Jon Hough <[email protected]> wrote:
> Hi Bob,
> What I want is to get certain columns of the array. I know I can use {."1 to
> do this. But then I might want to get the first three columns and also the
> first 4 columns as the output.I understand that to have my verb return the
> first 3 columns and also the first 4 columns, I need to use boxing. But my
> problem seems to be in the actual loop {"1, which is the part I am confused
> about.I can't do 3 4{"(0 1) arr because the output shapes are different, but
> I am sure there is a way to do things like this.
>
> Your suggestion:
> (3&{."1 ; 4&{.) arr
> gives what I was after. However if I wanted to get an arbitrary number of
> columns, the above becomes unwieldy unless I try something like:
> columns =: 3 4 5 4 5 NB. extract the first 3,4,5,4,5 columns respectively
> ;/columns{."(0 1) arr
> I get a length error trying my above code. Hmm...
>
>> From: [email protected]
>> Date: Fri, 26 Sep 2014 10:03:52 -0700
>> To: [email protected]
>> Subject: Re: [Jprogramming] Length errors when getting multiple columns from
>> array
>>
>> Hi Jon,
>>
>> I am a bit confused about what you would like as well, but without boxing
>> you could do this
>>
>> (3&{. , 4&{.)"1 arr
>> 0 1 2 0 1 2 3
>> 6 7 8 6 7 8 9
>> 2 3 4 2 3 4 5
>> 8 9 0 8 9 0 1
>> 4 5 6 4 5 6 7
>> 0 1 2 0 1 2 3
>> 6 7 8 6 7 8 9
>> 2 3 4 2 3 4 5
>> 8 9 0 8 9 0 1
>> 4 5 6 4 5 6 7
>>
>> but I am suspicious of the term 4 elements, so that what you may really want
>> is this
>>
>> (3&{."1 ; 4&{.) arr
>> ┌─────┬───────────┐
>> │0 1 2│0 1 2 3 4 5│
>> │6 7 8│6 7 8 9 0 1│
>> │2 3 4│2 3 4 5 6 7│
>> │8 9 0│8 9 0 1 2 3│
>> │4 5 6│ │
>> │0 1 2│ │
>> │6 7 8│ │
>> │2 3 4│ │
>> │8 9 0│ │
>> │4 5 6│ │
>> └─────┴───────────┘
>>
>> Cheers, bob
>>
>> On Sep 26, 2014, at 9:51 AM, Devon McCormick <[email protected]> wrote:
>>
>>> Not entirely sure what you want, but is this it?
>>>
>>> 3 4{."1&.><arr
>>> +-----+-------+
>>> |0 1 2|0 1 2 3|
>>> |6 7 8|6 7 8 9|
>>> |2 3 4|2 3 4 5|
>>> |8 9 0|8 9 0 1|
>>> |4 5 6|4 5 6 7|
>>> |0 1 2|0 1 2 3|
>>> |6 7 8|6 7 8 9|
>>> |2 3 4|2 3 4 5|
>>> |8 9 0|8 9 0 1|
>>> |4 5 6|4 5 6 7|
>>> +-----+-------+
>>>
>>>
>>> On Fri, Sep 26, 2014 at 12:44 PM, Jon Hough <[email protected]> wrote:
>>>
>>>> I have a 2-d array. e.g.
>>>> arr =: 10 6 $ i. 10
>>>> I want to get the first 3 columns from the array, e.g. 3{."1and get the
>>>> first 4 elements, e.g. 4{."1
>>>> However, combining these, as in
>>>> 3 4 {."(0 1) arrgives a length error. Of course 3{. and 4{. will give
>>>> different shape results so should be boxed and then concatenated
>>>> perhaps(?). I am not sure how to do this, but the end result I want would
>>>> be something like:
>>>>
>>>> ┌─────┐
>>>>
>>>> │0 1 2│
>>>>
>>>> │6 7 8│
>>>>
>>>> │2 3 4│
>>>>
>>>> │8 9 0│
>>>>
>>>> │4 5 6│
>>>>
>>>> │0 1 2│
>>>>
>>>> │6 7 8│
>>>>
>>>> │2 3 4│
>>>>
>>>> │8 9 0│
>>>>
>>>> │4 5 6│
>>>>
>>>> └─────┘
>>>>
>>>>
>>>> concatenated with
>>>>
>>>>
>>>> ┌───────┐│0 1 2 3││6 7 8 9││2 3 4 5││8 9 0 1││4 5 6 7││0 1 2 3││6 7 8 9││2
>>>> 3 4 5││8 9 0 1││4 5 6 7│
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> └───────┘
>>>>
>>>>
>>>>
>>>> ----------------------------------------------------------------------
>>>> For information about J forums see http://www.jsoftware.com/forums.htm
>>>
>>>
>>>
>>>
>>> --
>>> Devon McCormick, CFA
>>> ----------------------------------------------------------------------
>>> For information about J forums see http://www.jsoftware.com/forums.htm
>>
>> ----------------------------------------------------------------------
>> For information about J forums see http://www.jsoftware.com/forums.htm
>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
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