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https://issues.apache.org/jira/browse/MAHOUT-1602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14085487#comment-14085487
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Sean Owen commented on MAHOUT-1602:
-----------------------------------
Yeah, the comment is the one that's wrong. See
https://issues.apache.org/jira/browse/MAHOUT-847
> Euclidean Distance Similarity Math
> -----------------------------------
>
> Key: MAHOUT-1602
> URL: https://issues.apache.org/jira/browse/MAHOUT-1602
> Project: Mahout
> Issue Type: Bug
> Components: Collaborative Filtering, Math
> Reporter: Leonardo Fernandez Sanchez
>
> Within the file:
> /mrlegacy/src/main/java/org/apache/mahout/cf/taste/impl/similarity/EuclideanDistanceSimilarity.java
> Mentions that the implementation should be sqrt(n) / (1 + distance).
> Once the equation is simplified, should be:
> 1 / ((1 + distance) / sqrt(n))
> Coded:
> return 1.0 / ((1.0 + Math.sqrt(sumXYdiff2)) / Math.sqrt(n));
> But instead is (missing grouping brackets):
> 1 / (1 + distance / sqrt (n))
> Coded:
> return 1.0 / (1.0 + Math.sqrt(sumXYdiff2) / Math.sqrt(n));
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