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https://issues.apache.org/jira/browse/MAHOUT-923?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13168392#comment-13168392
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Ted Dunning commented on MAHOUT-923:
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Sean,
Clone can only return *exactly* the same type. This is a real problem
sometimes. For example, view matrices should not return view matrices but
should return something of the type of the underlying matrix, but in the right
size.
The issue is analogous to the problem with constructors compared to factory
methods. With constructors, you have already defined the return type and you
may not know enough to really choose the correct return type. With factory
methods, the framework is free to give you anything that satisfies the basic
contract.
> Row mean job for PCA
> --------------------
>
> Key: MAHOUT-923
> URL: https://issues.apache.org/jira/browse/MAHOUT-923
> Project: Mahout
> Issue Type: Improvement
> Components: Math
> Affects Versions: 0.6
> Reporter: Raphael Cendrillon
> Assignee: Raphael Cendrillon
> Fix For: Backlog
>
> Attachments: MAHOUT-923.patch, MAHOUT-923.patch
>
>
> Add map reduce job for calculating mean row (column-wise mean) of a
> Distributed Row Matrix for use in PCA.
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