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From "Becksfort, Jared" <Jared.Becksf...@STJUDE.ORG>
Subject RE: [math] Scaling arrays
Date Mon, 11 Mar 2013 17:28:25 GMT
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



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