Mike Seddon created SPARK-13097:
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             Summary: Extend Binarizer to allow Double AND Vector inputs
                 Key: SPARK-13097
                 URL: https://issues.apache.org/jira/browse/SPARK-13097
             Project: Spark
          Issue Type: Improvement
          Components: ML
            Reporter: Mike Seddon
            Priority: Minor


To enhance the existing SparkML Binarizer [SPARK-5891] to allow Vector in 
addition to the existing Double input column type.

A use case for this enhancement is for when a user wants to Binarize many 
similar feature columns at once using the same threshold value.

A real-world example for this would be where the authors of one of the leading 
MNIST handwriting character recognition entries converts 784 grayscale (0-255) 
pixels (28x28 pixel images) to binary if the pixel's grayscale exceeds 127.5: 
(http://arxiv.org/abs/1003.0358). With this modification the user is able to: 
VectorAssembler->Binarizer(127.5)->Classifier as all the pixels are of a 
similar type. 

This approach also allows much easier use of the ParamGridBuilder to test 
multiple theshold values.

I have already written the code and unit tests and have tested in a Multilayer 
perceptron classifier workflow.



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