[jira] [Reopened] (SPARK-9011) Spark 1.4.0| Spark.ML Classifier Output Formats Inconsistent --> Grid search working on LR but not on RF

["Shivam Verma (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-9011?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Shivam Verma reopened SPARK-9011:
---------------------------------

I did some more experiments. It is really a bug because pyspark.ml.tuning.CrossValidator seems to accept outputs of only certain classifiers. So it is the question of making a design choice: either ensuring consistency across classifier outputs in Spark.ML or making the BinaryClassificationEvaluator generic enough.
I have appropriately modified the description above and I am reopening the issue.

> Spark 1.4.0| Spark.ML Classifier Output Formats Inconsistent --> Grid search working on LR but not on RF
> --------------------------------------------------------------------------------------------------------
>
>                 Key: SPARK-9011
>                 URL: https://issues.apache.org/jira/browse/SPARK-9011
>             Project: Spark
>          Issue Type: Bug
>          Components: ML, MLlib, PySpark
>    Affects Versions: 1.4.0
>         Environment: Spark 1.4.0 standalone on top of Hadoop 2.3 on single node running CentOS
>            Reporter: Shivam Verma
>            Priority: Critical
>              Labels: cross-validation, ml, mllib, pyspark, randomforest, tuning
>
> Hi,
> I ran into this bug while using pyspark.ml.tuning.CrossValidator on an RF (Random Forest) classifier to classify a small dataset using the pyspark.ml.tuning module. (This is a bug because CrossValidator works on LR (Logistic Regression) but not on RF)
> Bug:
> There is an issue with how BinaryClassificationEvaluator(self, rawPredictionCol="rawPrediction", labelCol="label", metricName="areaUnderROC") interprets the 'rawPredict' column - with LR, the rawPredictionCol is expected to contain vectors, whereas with RF, the prediction column contains doubles. 
> Suggested Resolution: Either enable BinaryClassificationEvaluator to work with doubles, or let RF output a column rawPredictions containing the probability vectors (with probability of 1 assigned to predicted label, and 0 assigned to the rest).
> Detailed Observation:
> While running grid search on an RF classifier to classify a small dataset using the pyspark.ml.tuning module, specifically the ParamGridBuilder and CrossValidator classes. I get the following error when I try passing a DataFrame of Features-Labels to CrossValidator:
> {noformat}
> Py4JJavaError: An error occurred while calling o1464.evaluate.
> : java.lang.IllegalArgumentException: requirement failed: Column rawPrediction must be of type org.apache.spark.mllib.linalg.VectorUDT@1eef but was actually DoubleType.
> {noformat}
> I tried the following code, using the dataset given in Spark's CV documentation for [cross validator|https://spark.apache.org/docs/latest/api/python/pyspark.ml.html#pyspark.ml.tuning.CrossValidator]. I also pass the DF through a StringIndexer transformation for the RF:
>  
> {noformat}
> dataset = sqlContext.createDataFrame([(Vectors.dense([0.0]), 0.0),(Vectors.dense([0.4]), 1.0),(Vectors.dense([0.5]), 0.0),(Vectors.dense([0.6]), 1.0),(Vectors.dense([1.0]), 1.0)] * 10,["features", "label"])
> stringIndexer = StringIndexer(inputCol="label", outputCol="indexed")
> si_model = stringIndexer.fit(dataset)
> dataset2 = si_model.transform(dataset)
> keep = [dataset2.features, dataset2.indexed]
> dataset3 = dataset2.select(*keep).withColumnRenamed('indexed','label')
> rf = RandomForestClassifier(predictionCol="rawPrediction",featuresCol="features",numTrees=5, maxDepth=7)
> grid = ParamGridBuilder().addGrid(rf.maxDepth, [4,5,6]).build()
> evaluator = BinaryClassificationEvaluator()
> cv = CrossValidator(estimator=rf, estimatorParamMaps=grid, evaluator=evaluator)
> cvModel = cv.fit(dataset3)
> {noformat}
> Note that the above dataset *works* on logistic regression. I have also tried a larger dataset with sparse vectors as features (which I was originally trying to fit) but received the same error on RF.



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