# Re: [Jprogramming] converting numbers and rank trouble

```Roger said that the boxed sample was only for illustration. But then, where
does the empty box come from? Or is this a comma or tab delimited file?
Granted, if the original file is pretty trashy then it is probably
necessary to do some clean-up ending out in table of boxes. But if the data
is relatively clean, then maybe skip the boxing step. Something like:```
```
data=:0 : 0

2 11 xxx 9

3_ -1 11 3j

)

_&".;._2 data

2 11 _ 9

_ _1 11 _
​

On Fri, Apr 13, 2018 at 2:04 PM, Joe Bogner <joebog...@gmail.com> wrote:

> Don - the source data is a text file of float data that is being read into
> J
>
> Roger - thanks, for the confirmation. I find that when I'm way from J/APL
> for awhile, my mind drifts back into "if/then" thinking instead of the
> simpler and faster method of using multiplication where possible. I fiddled
> with ^: and @. for over an hour until I posted here, and then in a moment
> of odd clarity the multiplication idea hit
>
> Somewhat tangential -- I recently had to do quantity conversions
>
> QuantitySF = IF(UOM="SF",Quantity,UOM="SY",Quantity*9,0)
>
> Beautifully (in my opinion) represented as:
>
>   qtysf =. qty*(1,9,0) {~ idotfill (>'SF';'SY');uom
>
> I'm not nearly as good at keeping references, but this has been highlighted
> before I think as a hallmark of APL/J elsewhere. I will have to read
> through the Knuth paper linked
>
>
>
>
> On Fri, Apr 13, 2018 at 3:47 PM, Roger Hui <rogerhui.can...@gmail.com>
> wrote:
>
> > Yes, it's a boon that 0 * x is 0 for any x.  Some authors go even
> further:
> > Knuth propose to have 0 * x be 0 even when x is an expression which is in
> > error.  He wanted this to make "Iverson's convention" work in more
> > situations.  See https://arxiv.org/PS_cache/math/pdf/9205/9205211v1.pdf
> >
> >
> >
> > On Fri, Apr 13, 2018 at 12:24 PM, Joe Bogner <joebog...@gmail.com>
> wrote:
> >
> > > 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
> > > >
> > > > 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
> > > >> > ------------------------------------------------------------
> > > ----------
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> > > forums.htm
> > > >> ------------------------------------------------------------
> > ----------
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> > forums.htm
> > > >>
> > > >
> > > >
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> > >
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> >
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For information about J forums see http://www.jsoftware.com/forums.htm```