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Date: Fri, 15 Mar 2013 14:47:31 -0700
From: Phil Steitz <phil.steitz@gmail.com>
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To: Commons Developers List <dev@commons.apache.org>
Subject: Re: [math] Scaling arrays
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On 3/15/13 1:21 PM, Becksfort, Jared wrote:
>
> -----Original Message-----
> From: Becksfort, Jared
> Sent: Monday, March 11, 2013 12:28 PM
> To: Commons Developers List
> Subject: RE: [math] Scaling arrays. .
>
> On 3/11/13 8:21 AM, Becksfort, Jared wrote:
>> Hi Phil,
>>
>>> What exactly *is* it and what are the use cases?
>> Just a method to multiply each element in an array by a number and return either a copy of the array or do it in place.  Maybe there can be one method for either way:
>>
>> public static double[] scale(double val, final double[] arr) {
>>         double[] newArr = new double[arr.length];
>>         for (int i = 0; i < arr.length; i++) {
>>             newArr[i] = arr[i] * val;
>>         }
>>         return newArr;
>>     }
>>
>>     public static void scaleInPlace(double val, final double[] arr) {
>>         for (int i = 0; i < arr.length; i++) {
>>             arr[i] *= val;
>>         }
>>     }
>>
>>> ...use cases
>> I imagine they are pretty varied.  These methods could be used any time you want to multiply all elements in an array by a number without writing a loop each time.  I am using this in some optimization code that I am submitting but figured it would be broadly applicable enough to just be put in the MathArrays class.
>>
>> Jared
>>
>> -----Original Message-----
>> From: Phil Steitz [mailto:phil.steitz@gmail.com]
>> Sent: Sunday, March 10, 2013 2:19 PM
>> To: Commons Developers List
>> Subject: Re: [math] Scaling arrays. .
>>
>> On 3/8/13 12:14 PM, Becksfort, Jared wrote:
>>> Hello,
>>>
>>> I may be missing it somewhere, but I am surprised there is no function for scaling arrays in MathArrays.java or somewhere else.
>>>
>>> -          Am I stupidly missing it?
>> Probably not.  Closest thing is probably normalize in MathArrays.
>>> -          Is there a reason it is not in there?
>> Probably no; though you will find that most vector / array algebraic operations are implemented on the objects in the linear package, rather than directly on double[]s.
>>> -          Shall I add it?
>> +1 to add this
>> Created an issue and submitted patches for MathArrays.java and MathArraysTest.java
>> https://issues.apache.org/jira/browse/MATH-946
>> Jared
>> Phil
>> What exactly *is* it and what are the use cases?
>>
>> Phil
>>> Thanks,
>>> Jared
> Hello,
>
> Does anyone know if these changes might be committed to the repository?  Some upcoming changes I am submitting for another issue rely on it.  It is not too much trouble for me to remove the dependencies, but if this is going in then I may as well use it.
>
> https://issues.apache.org/jira/browse/MATH-946

Patches just applied.  Many thanks.  One small thing that will make
it easier in the future is to create patches from the top-level
/trunk directory.  Thanks!

Phil
>
> Thanks,
> Jared
>
>
>
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