Dominik Dahlem created SPARK-11284:
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             Summary: ALS produces predictions as floats and should be double
                 Key: SPARK-11284
                 URL: https://issues.apache.org/jira/browse/SPARK-11284
             Project: Spark
          Issue Type: Bug
          Components: ML
    Affects Versions: 1.5.1
         Environment: All
            Reporter: Dominik Dahlem


Using pyspark.ml and DataFrames, The ALS recommender cannot be evaluated using 
the RegressionEvaluator, because of a type mis-match between the model 
transformation and the evaluation APIs. One can work around this by casting the 
prediction column into double before passing it into the evaluator. However, 
this does not work with pipelines and cross validation.

Code and traceback below:

{code}
        als = ALS(rank=10, maxIter=30, regParam=0.1, userCol='userID', 
itemCol='movieID', ratingCol='rating')
        model = als.fit(training)
        predictions = model.transform(validation)
        evaluator = RegressionEvaluator(predictionCol='prediction', 
labelCol='rating')
        validationRmse = evaluator.evaluate(predictions, {evaluator.metricName: 
'rmse'})
{code}

Traceback:
    validationRmse = evaluator.evaluate(predictions, {evaluator.metricName: 
'rmse'})
  File 
"/Users/dominikdahlem/software/spark-1.6.0-SNAPSHOT-bin-custom-spark/python/lib/pyspark.zip/pyspark/ml/evaluation.py",
 line 63, in evaluate
  File 
"/Users/dominikdahlem/software/spark-1.6.0-SNAPSHOT-bin-custom-spark/python/lib/pyspark.zip/pyspark/ml/evaluation.py",
 line 94, in _evaluate
  File 
"/Users/dominikdahlem/software/spark-1.6.0-SNAPSHOT-bin-custom-spark/python/lib/py4j-0.9-src.zip/py4j/java_gateway.py",
 line 813, in __call__
  File 
"/Users/dominikdahlem/projects/repositories/spark/python/pyspark/sql/utils.py", 
line 42, in deco
    raise IllegalArgumentException(s.split(': ', 1)[1])
pyspark.sql.utils.IllegalArgumentException: requirement failed: Column 
prediction must be of type DoubleType but was actually FloatType.




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