Minor Description
Params.validateParams() can not be called automatically currently. Such as the following code snippet will not throw exception which is not as expected.
val df = sqlContext.createDataFrame(
Seq(
(1, Vectors.dense(0.0, 1.0, 4.0), 1.0),
(2, Vectors.dense(1.0, 0.0, 4.0), 2.0),
(3, Vectors.dense(1.0, 0.0, 5.0), 3.0),
(4, Vectors.dense(0.0, 0.0, 5.0), 4.0))
).toDF("id", "features", "label")
val scaler = new MinMaxScaler()
.setInputCol("features")
.setOutputCol("features_scaled")
.setMin(10)
.setMax(0)
val pipeline = new Pipeline().setStages(Array(scaler))
pipeline.fit(df)
validateParams() should be called by PipelineStage(Pipeline/Estimator/Transformer) automatically, so I propose to put it in transformSchema().
