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From feynmanliang <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-9893] user guide for VectorSlicer
Date Tue, 18 Aug 2015 20:08:34 GMT
Github user feynmanliang commented on a diff in the pull request:

    https://github.com/apache/spark/pull/8267#discussion_r37346802
  
    --- Diff: docs/ml-features.md ---
    @@ -1389,3 +1389,145 @@ print(output.select("features", "clicked").first())
     
     # Feature Selectors
     
    +## VectorSlicer
    +
    +`VectorSlicer` is a transformer that takes a feature vector and outputs a new feature
vector with a sub-array of the original features. It is useful for extracting features from
a vector column.
    +
    +`VectorSlicer` accepts a vector column with a specified indices, then outputs a new vector
column whose values are selected via those indices. There are two types of indices, 
    +
    + 1. Integer indices that represents the real indices in the vector, `setIndices()`;
    +
    + 2. String indices that represents the names of features in the vector, `setNames()`.
    +
    +Specify by integer and string are both acceptable, moreover, you can use integer index
and string name simultaneously. At least one feature must be selected. Duplicate features
are not allowed, so there can be no overlap between selected indices and names. Note that
if names of features are selected, an exception will be threw out when encountering with empty
input attributes.
    --- End diff --
    
    nit: ***Specification*** by integer and string are both acceptable***. M***oreover,


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