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https://issues.apache.org/jira/browse/SPARK-5133?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14648565#comment-14648565
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Joseph K. Bradley commented on SPARK-5133:
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Yes, that's the approach I was planning on taking.  I realized that this JIRA 
is blocked by the one I just linked; I'll try to get it merged ASAP.  I 
appreciate your offer to contribute it, and I would normally say yes, but I'm a 
bit panicked by the code freeze.  Since I'm very familiar with the tree code, 
would you mind letting me send it, and helping to review my PR once I send one?

If you are interested, it would be great to collaborate to add better methods 
of measuring feature importance (or other features) for the next release cycle.

Thanks again!

> Feature Importance for Decision Tree (Ensembles)
> ------------------------------------------------
>
>                 Key: SPARK-5133
>                 URL: https://issues.apache.org/jira/browse/SPARK-5133
>             Project: Spark
>          Issue Type: New Feature
>          Components: ML, MLlib
>            Reporter: Peter Prettenhofer
>   Original Estimate: 168h
>  Remaining Estimate: 168h
>
> Add feature importance to decision tree model and tree ensemble models.
> If people are interested in this feature I could implement it given a mentor 
> (API decisions, etc). Please find a description of the feature below:
> Decision trees intrinsically perform feature selection by selecting 
> appropriate split points. This information can be used to assess the relative 
> importance of a feature. 
> Relative feature importance gives valuable insight into a decision tree or 
> tree ensemble and can even be used for feature selection.
> More information on feature importance (via decrease in impurity) can be 
> found in ESLII (10.13.1) or here [1].
> R's randomForest package uses a different technique for assessing variable 
> importance that is based on permutation tests.
> All necessary information to create relative importance scores should be 
> available in the tree representation (class Node; split, impurity gain, 
> (weighted) nr of samples?).
> [1] 
> http://scikit-learn.org/stable/modules/ensemble.html#feature-importance-evaluation



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