[jira] [Commented] (MAHOUT-1239) Standardize form of log-likelihood computation

["Ted Dunning (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAHOUT-1239?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13673617#comment-13673617 ] 

Ted Dunning commented on MAHOUT-1239:
-------------------------------------

Looks fine to me.  Go ahead and drop it in.
                
> Standardize form of log-likelihood computation
> ----------------------------------------------
>
>                 Key: MAHOUT-1239
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-1239
>             Project: Mahout
>          Issue Type: Improvement
>    Affects Versions: 0.7
>            Reporter: Sean Owen
>            Assignee: Sean Owen
>            Priority: Minor
>             Fix For: 0.8
>
>         Attachments: MAHOUT-1239.patch
>
>
> qzchenwl@gmail.com reported that LogLikelihood.logLikelihoodRatio() looked like its formula was incorrect, at least with respect to http://tdunning.blogspot.mx/2008/03/surprise-and-coincidence.html
> It appears that the calculation is correct but in a different form, that is not immediately recognizable as correct. The proposal here is to change the code to match the blog post and avoid confusion (and ends up avoiding 2 method calls).
> (Along the way, I think this fixes a tiny other problem in a related test. We have a test case that detects when round-off would produce a negative LLR and should be clamped to 0, but the test asserts that the result is >0 not >=0.)

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