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From "jason (JIRA)" <>
Subject [jira] Created: (MATH-212) Provide a way to copy all instances of StorelessUnivariateStatistic (e.g. Mean, Variance, Max, Kurtoise, etc), perhaps via a copy-constructor
Date Mon, 23 Jun 2008 00:21:45 GMT
Provide a way to copy all instances of StorelessUnivariateStatistic (e.g. Mean, Variance, Max,
Kurtoise, etc), perhaps via a copy-constructor

                 Key: MATH-212
             Project: Commons Math
          Issue Type: Improvement
         Environment: N/A
            Reporter: jason
            Priority: Minor
         Attachments: copy_constructor.patch

Below is the conversation related to this topic that was posted to the Commons Users group.
As soon as I figure out how, I'll attach my patch that adds copy constructors to all intended
classes exception GeometricMean and SummaryStatistic, which both allow the user to specify
arbitrary implementations and thus cannot be copied. See below for details.


Well, that was easy in some cases and I'm not sure how it went in others and could use help.
I had issue with creating a copy constructor for GeometricMean and SummaryStatistic. Both
of these classes allow the user to, via the API, set a StorelessUnivariateStatistic as the
implementation. For instance take the following method in Geometric mean:

   public void setSumLogImpl(
           StorelessUnivariateStatistic sumLogImpl) {
       this.sumOfLogs = sumLogImpl;

There is no way to create a true deep copy of sumLogImpl, as we only know it to be an instance
of StorelessUnivariateStatistic. I think the solution is to allow the copy constructors for
the below classes into the baseline, but not provide a copy constructor for GeometricMean
or SummaryStatistic unless you want to (1) deprecate the implementation business or (2) create
a abstract copy method in StorelessUnivariateStatistic forcing all implementations to be 'copyable'.

The following classes were able to be given copy constructors without issue:

Phil Steitz wrote:
> Jason C. HandUber wrote:
>> Hello,
>> I'm writing an evolutionary algorithm in which each individual contains StandardDeviations
and Means. From time to time I need a deep copy / clone of an individual. Thus far I've actually
had to keep a list of all data and, when cloning, generate a new statistic and increment it
with all that data. Now that I'm moving to production level, turns out I'm running out of
memory (no huge surprise). I'm going to extend Mean, Variance, StandardDeviation, FirstMoment,
and SecondMoment for my application to provide a copy constructor (which, according to Item
10, page 51 of Bloch's effective java, beats out clone, and I buy that) for each. Anyway,
I think that addition would be easy and general enough to introduce into the trunk. Any thoughts?
> +1 on this enhancement, also for SummaryStatistics, implemented as you describe.
> Please follow instructions here <>
to create a patch against either trunk or the 2.0 development branch (/branches/MATH_2_0)
and attach it to a JIRA ticket.
> Thanks!
> Phil 

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