[jira] [Updated] (MAHOUT-1602) Euclidean Distance Similarity Math

["Andrew Palumbo (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MAHOUT-1602?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrew Palumbo updated MAHOUT-1602:
-----------------------------------
    Labels: legacy  (was: )

> 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
>              Labels: legacy
>
> 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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