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From Phil Steitz <stei...@yahoo.com>
Subject Re: cvs commit: jakarta-commons-sandbox/math/src/test/org/apache/commons/math/stat
Date Tue, 17 Jun 2003 08:06:31 GMT

--- "Mark R. Diggory" <mdiggory@latte.harvard.edu> wrote:
> Al Chou wrote:
> 
> >--- mdiggory@apache.org wrote:
> >  
> >
> >>mdiggory    2003/06/16 07:29:31
> >>
> >>  Modified:    math/xdocs developers.xml
> >>               math/src/java/org/apache/commons/math/stat
> >>                        UnivariateImpl.java
> >>               math/src/test/org/apache/commons/math/stat
> >>                        CertifiedDataTest.java
> >>  Log:
> >>  PR: http://nagoya.apache.org/bugzilla/show_bug.cgi?id=20782
> >>  Submitted by:	HotFusionMan@Yahoo.com
> >>  
> >>  I added this, but there are changes I'd like to make in the near future.
> >>Only the "running" aspects of the variance calc should be in the
> insertValue
> >>function, all other calculation should be in the getVariance function.
> >>    
> >>
> >
> >OK, that sounds reasonable.  Also, I was starting an Extract Method
> refactoring
> >to reduce duplication among the windowSize != n and infinite window branches
> of
> >insertValue.
> >
> >
> >Al
> >
> 
> Yes, this is the direction I am working on as well. Lets try to 
> coordinate our efforts.
> 
> (1) I'm looking to setup "true deligation" where UnivariateImpl is 
> actually an extension of AbstractStoreUnivariate and deligates to these 
> methods when doing stored processing. This would simply look like:
> 
>     /**
>      * @see org.apache.commons.math.stat.Univariate#getMean()
>      */
>     public double getMean() {
>         if (windowSize != Univariate.INFINITE_WINDOW) {
>           return super.getMean();
>         }
>        
>         return mean;
>     }

-1  I would prefer for both to delegate to an optimized method in StatUtils.
> 
> (2) I want to apply the same strategy used in your mean and variance 
> calculations for skew and kurt. The getters for these properties then 
> would truely just be "getters" without the calculations occuring in them 
> as well. This means the sum of powers code goes away for now.
> 
> (3) I want to derive an methodology for the same two-pass algorithm for 
> skew and kurt, hey, if we can't find published work on it, then theres a 
> possibly paper in the future for someone to write!
> 
We should stick with established algorithms.  I would suggest researching
established computational formulas for higher order moments.


> -Mark
> 
> 
> 
> 
> 
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