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Date: Fri, 6 May 2011 14:35:03 +0000 (UTC)
From: "Grant Ingersoll (JIRA)" <jira@apache.org>
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Subject: [jira] [Updated] (MAHOUT-688) High Document Frequency pruning for
 seq2sparse
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     [ https://issues.apache.org/jira/browse/MAHOUT-688?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Grant Ingersoll updated MAHOUT-688:
-----------------------------------

    Attachment: MAHOUT-688.patch

Reorgs the code a little bit to move std. dev. calculation to a common place.  Also, puts in tests for std. dev. and fixes the std. dev. calculation, which _I am pretty sure_ was incorrectly calculated (it was missing the subtraction of the average in the sum of squares calc). Also added license headers and cleaned up the formatting a bit.

Since we are in code freeze, we can iterate on this a bit for 0.6.


> High Document Frequency pruning for seq2sparse
> ----------------------------------------------
>
>                 Key: MAHOUT-688
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-688
>             Project: Mahout
>          Issue Type: Improvement
>            Reporter: Vasil Vasilev
>            Assignee: Grant Ingersoll
>            Priority: Minor
>              Labels: Vectorization
>             Fix For: 0.6
>
>         Attachments: MAHOUT-688.patch, MAHOUT-688.patch
>
>
> This improvement allows to prune the words with high document frequencies from the tf and tf-idf vectors produced by seq2sparse, based on the standard deviation of the words' document frequencies and specifying which rods to be pruned in a means of times this standard deviation. One good option is 3 times the standard deviation

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