Well, I stumbled upon a fast way that takes advantage of simple
multiplication
_ * 0 = 0
_ * 1 = _
5 * 1 = 5
_3 {. (-.@isblank * _&".) c1
1.01 _ 0
(6!:2) '(isblank * _&".) c1'
1.00593
I'm still interested in alternatives that are similar speed if possible
On Fri, Apr 13, 2018 at 3:19 PM, Joe Bogner <joebog...@gmail.com> wrote:
> Thank you -- Yes, I didn't want to send along the full sample, although I
> could have created some dummy data.
>
> Both Don and Raul's method are similar and are equally slow as the way I
> had
>
> It's not terribly important but I have like 10 numeric columns that I
> convert in a script and have to painfully wait 30 seconds each time I run
> the script. If I could shave 20 seconds off something that I seem to be
> running multiple times a day and learn something in the process, I figured
> it was worthwhile to ask
>
> (6!:2) '{.@(_&".)"1 c'
> 3.44371
>
> Here's a reasonable approximation:
>
> c1 =. 1.5e6 # (>' ';'bad';'10')
>
>
> c1=: (((5e6,4)$'1.01'),'bad'),' '
> $ c1
> 5000002 4
> (6!:2) '{.@(_&".)"1 c1'
> 3.29915
>
>
> Compare to
>
> (6!:2) '_ ". c1'
> 1.01854
>
> _3 {. _ ". c1 NB. bad values at the end... ideally the blank is 0 though
> 1.01 _ _
>
>
> On Fri, Apr 13, 2018 at 2:13 PM, Raul Miller <rauldmil...@gmail.com>
> wrote:
>
>> Your sample data does not match your problem description.
>>
>> That said,
>>
>> {.@(_&".)"1 > ' ';'bad';'10'
>> 0 _ 10
>>
>> Thanks,
>>
>> --
>> Raul
>>
>>
>> On Fri, Apr 13, 2018 at 2:03 PM, Joe Bogner <joebog...@gmail.com> wrote:
>> > I have a large byte array that I want to convert to a number array. I
>> want
>> > to use _ to indicate a bad value, but blank should be treated as 0
>> >
>> > $ c
>> > 4862343 10
>> >
>> > Instead of this:
>> >
>> > asnumber =: _&".
>> >
>> > asnumber (>' ';'bad';'10')
>> > _ _ 10
>> >
>> > I want this:
>> >
>> >
>> > asnumber (>' ';'bad';'10')
>> > 0 _ 10
>> >
>> > This works, but is much slower than I'd like -- nearly 3x slower than
>> just
>> > _ ".
>> >
>> > asnumber =: _ ". '0' ,~^:([: */ ' '&=@])"1 ]
>> > asnumber (>' ';'bad';'10')
>> > 0 _ 10
>> >
>> > (6!:2) 'asnumber c'
>> > 3.32579
>> > (6!:2) '_&". c'
>> > 1.35091
>> >
>> >
>> > I have an isblank function that is fast
>> >
>> > isblank =. ([: ({. -:"1 }.) ' '&,)
>> > (6!:2) 'isblank c'
>> > 0.033164
>> >
>> > I can't seem to combine the two into something that performs well
>> without
>> > doing things at the atom/row level instead of the entire array. I
>> suspect
>> > I'm getting tripped up by rank
>> > ----------------------------------------------------------------------
>> > 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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