Github user feynmanliang commented on a diff in the pull request: https://github.com/apache/spark/pull/8267#discussion_r37346906 --- 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()`. --- End diff -- Document that this requires the vector column to have an `AttributeGroup` since the implementation matches on the `name` field of an `Attribute`
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