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https://issues.apache.org/jira/browse/MAHOUT-880?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13165462#comment-13165462
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Dmitriy Lyubimov commented on MAHOUT-880:
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I think rowMeans approach is still suboptimal for my use case (MAHOUT-817). It
is possible i don't understand something about DRM though.
The DRM formation as a solver requires knowledge of num rows and num columns.
This is technically never required for any operation in PCA (including
colMeans() ) and in many cases also impractical as previous pipeline jobs don't
necessarily calculate those.
Nor does SSVD require preliminary knowledge of matrix dimensions.
Ideally, in PCA flow we want to compute pairs (numRows, sumRows) for each
reducer output and then have a front-end routine to finish reducing that to
just one mean row.
> Add some matrix method(like addition, subtraction, norm ... etc) to
> DistributedRowMatrix
> ----------------------------------------------------------------------------------------
>
> Key: MAHOUT-880
> URL: https://issues.apache.org/jira/browse/MAHOUT-880
> Project: Mahout
> Issue Type: New Feature
> Components: Math
> Affects Versions: 0.6
> Reporter: Wangda Tan
> Priority: Minor
> Labels: DistributedRowMatrix
> Attachments: MAHOUT-880.patch, MAHOUT-880.patch, MAHOUT-880.patch
>
>
> I'm a new to Mahout, I didn't find some basic matrix functions. This make
> users cannot do many tasks by CLI or API, if user get some result through
> existing map-reduce matrix operation (like svd), he cannot do farther steps.
> I make a list for it:
> 1) Addition, Subtraction
> 2) Norm (like norm-1, norm-2, norm-frobenius)
> 3) Matrix compare
> 4) Get lower triangle, upper triangle and diagonal
> 5) Get identity and zero matrix
> 6) Put two or matrix to together: A = [A1, A2]
> 7) More linear equations solver method, like Gaussian elimination (maybe it's
> hard to implement)
> 8) import and export CSV, ARFF ... (this will very useful when user want to
> reuse result from or to other applications like MATLAB)
> I want to know is there any plan to do this, if so, I can make some efforts
> to implement these.
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