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From "Luc Maisonobe (JIRA)" <j...@apache.org>
Subject [jira] [Reopened] (MATH-817) Multivariate Normal Mixture Model Fitting by Expectation Maximization
Date Fri, 29 Mar 2013 07:43:15 GMT
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[ https://issues.apache.org/jira/browse/MATH-817?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Luc Maisonobe reopened MATH-817:
--------------------------------

As I was doing the release for 3.2, findbugs identified some problems.

There are integer divisions which are assumed to be floating number divisions in the estimate
method near line 338.
These divisions are used to compute min and max indices for a bin and are in fact converted
back to integer. So I guess the intermediate double could be completely removed.

When one wants to compute (int) floor(p/q) and p and q are both positive integers, then p/q
already is the appropriate result.
When one wants to compute (int) ceil(p/q)  and p and q are both positive integers, then (p
+ q - 1)/q could be used.

So I would like to change the two computations to:
{code}
// minimum index from sorted data for this bin
final int minIndex = FastMath.max(0, ((binNumber - 1) * numRows) / totalBins);

// maximum index from sorted data for this bin
final int maxIndex = (binNumber * numRows + numComponents - 1) / numComponents - 1;
{code}

Does this change seems reasonable?

> Multivariate Normal Mixture Model Fitting by Expectation Maximization
> ---------------------------------------------------------------------
>
>                 Key: MATH-817
>                 URL: https://issues.apache.org/jira/browse/MATH-817
>             Project: Commons Math
>          Issue Type: New Feature
>            Reporter: Jared Becksfort
>            Priority: Minor
>             Fix For: 3.2
>
>         Attachments: math_817.patch, MultivariateNormalMixtureExpectationMaximizationFitter.java,
MultivariateNormalMixtureExpectationMaximizationFitterTest.java, MultivariateNormalMixtureExpectationMaximizationTest.java.patch
>
>   Original Estimate: 1m
>  Remaining Estimate: 1m
>
> I will submit a class for fitting Multivariate Normal Mixture Models using Expectation
Maximization.
> > Hello,
> >
> > I have implemented some classes for multivariate Normal distributions, multivariate
normal mixture models, and an expectation maximization fitting class for the mixture model.
I would like to submit it to Apache Commons Math.  I still have some touching up to do so
that they fit the style guidelines and implement the correct interfaces.  Before I do so,
I thought I would at least ask if the developers of the project are interested in me submitting
them.
> >
> > Thanks,
> > Jared Becksfort
> Dear Jared,
> Yes, that would be very nice to have such an addition! Remember to also include unit
tests (refer to the current ones for examples). The best would be to split a submission up
into multiple minor ones, each covering a natural submission (e.g. multivariate Normal distribution
in one submission), and create an issue as described at http://commons.apache.org/math/issue-tracking.html
.
> If you run into any problems, please do not hesitate to ask on this mailing list.
> Cheers, Mikkel.

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