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Re: Re: Setting Negatives to Zero

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82858] Re: [mg82803] Re: [mg82736] Setting Negatives to Zero
  • From: DrMajorBob <drmajorbob at bigfoot.com>
  • Date: Thu, 1 Nov 2007 05:20:19 -0500 (EST)
  • References: <7189487.1193744482274.JavaMail.root@m35> <op.t00vb4u2qu6oor@monster.gateway.2wire.net> <18551847.1193774194904.JavaMail.root@m35> <200710311115.GAA22532@smc.vnet.net> <7757409.1193865583328.JavaMail.root@m35>
  • Reply-to: drmajorbob at bigfoot.com

No mapping needed here:

Clip[Table[Range[-5,5],{5},{3}],{0,10}]

{{{0,0,0,0,0,0,1,2,3,4,5},{0,0,0,0,0,0,1,2,3,4,5},{
     0,0,0,0,0,0,1,2,3,4,5}},{{0,0,0,0,0,0,1,2,3,4,5},{0,0,0,0,0,0,1,2,3,4,5},{
       0,0,0,0,0,0,1,2,3,4,5}},{{0,0,0,0,0,0,1,2,3,4,5},{0,0,0,0,0,0,1,2,3,
       4,5},{0,0,0,0,0,0,1,2,3,4,5}},{{0,0,0,0,0,0,1,2,3,4,5},{0,0,0,0,0,0,1,2,
       3,4,5},{0,0,0,0,0,0,1,2,3,4,5}},{{0,0,0,0,0,0,1,2,3,4,5},{0,0,0,0,0,0,1,
       2,3,4,5},{0,0,0,0,0,0,1,2,3,4,5}}}

$Version

5.2 for Microsoft Windows (June 20, 2005)

An infinite upper limit does NOT work in v5.2, however:

Clip[Table[Range[-5,5],{5},{3}],{0,Infinity}]

Clip[{{{-5,-4,-3,-2,-1,0,1,2,3,4,5},{-5,-4,-3,-2,-1,0,1,2,3,4,
         5},{-5,-4,-3,-2,-1,0,1,2,3,4,5}},{{-5,-4,-3,-2,-1,0,1,2,3,
         4,5},{-5,-4,-3,-2,-1,0,1,2,3,4,5},{-5,-4,-3,-2,-1,0,1,2,3,
         4,5}},{{-5,-4,-3,-2,-1,0,1,2,3,4,5},{-5,-4,-3,-2,-1,0,1,2,3,4,
         5},{-5,-4,-3,-2,-1,0,1,2,3,4,5}},{{-5,-4,-3,-2,-1,0,1,2,3,
         4,5},{-5,-4,-3,-2,-1,0,1,2,3,4,5},{-5,-4,-3,-2,-1,0,1,2,3,
         4,5}},{{-5,-4,-3,-2,-1,0,1,2,3,4,5},{-5,-4,-3,-2,-1,0,1,2,3,4,
         5},{-5,-4,-3,-2,-1,0,1,2,3,4,5}}},{0,â??}]

It does work in v6.

Bobby

On Wed, 31 Oct 2007 12:53:37 -0500, János <janos.lobb at yale.edu> wrote:

> It does not work in 5.2, unless I Map it to the list at Level {2}. Like
>
> Map[Clip[#,{0,Max[lst]}]&,lst, {2}]
>
> or something similar.
>
> János
>
> On Oct 31, 2007, at 7:15 AM, DrMajorBob wrote:
>
>> But Clip isn't Listable!
>>
>> Attributes@Clip
>>
>> {NumericFunction, Protected}
>>
>> So how could that work? But it does, evidently:
>>
>> Clip[Range@100, {5, 95}]
>>
>> {5, 5, 5, 5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, \
>> 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, \
>> 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, \
>> 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, \
>> 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, \
>> 88, 89, 90, 91, 92, 93, 94, 95, 95, 95, 95, 95, 95}
>>
>> Yet another undocumented feature.
>>
>> Bobby
>>
>> On Tue, 30 Oct 2007 14:54:09 -0500, Kevin J. McCann
>> <Kevin.McCann at umbc.edu> wrote:
>>
>>> Thanks, Bobby.
>>>
>>> Carl Woll gave me the following way to do it.
>>>
>>> Clip[data,{0,Infinity}]
>>>
>>> It works and is fast. I had never used Clip before - actually, I didn't
>>> know about it.
>>>
>>> Kevin
>>>
>>> DrMajorBob wrote:
>>>> data = data /. x_?Negative -> 0
>>>>
>>>> or something like
>>>>
>>>> Attributes[negToZero]={Listable}
>>>> negToZero[x_?NumericQ] = Sign[x] x
>>>> data = negToZero@data
>>>>
>>>> Bobby
>>>>
>>>> On Tue, 30 Oct 2007 03:26:37 -0500, Kevin J. McCann
>>>> <Kevin.McCann at umbc.edu> wrote:
>>>>
>>>>> I have a very large data set (64000 x 583) in which negative values
>>>>> indicate "no data", unfortunately these negatives are not all the  
>>>>> same.
>>>>> I would like to efficiently set all these negatives to zero. I know
>>>>> that
>>>>> I will likely be embarrassed when I see how to do it, but I can't  
>>>>> seem
>>>>> to remember or figure it out. I should emphasize that because of the
>>>>> size of the data set, this needs to be done efficiently. Another
>>>>> programming language does it as follows:
>>>>>
>>>>>         x(x < 0) = 0;
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Kevin
>>>>
>>>>
>>>>
>>>
>>
>>
>>
>> --
>> DrMajorBob at bigfoot.com
>
>
>
> ----------------------------------------------
> Trying to argue with a politician is like lifting up the head of a  
> corpse.
> (S. Lem: His Master Voice)
>
>



-- 
DrMajorBob at bigfoot.com


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