[SPARK-8711] [ML] Add additional methods to PySpark ML tree models

Add numNodes and depth to treeModels, add treeWeights to ensemble Models.
Add __repr__ to all models.

Author: MechCoder <manojkumarsivaraj334@gmail.com>

Closes #7095 from MechCoder/missing_methods_tree and squashes the following commits:

23b08be [MechCoder] private [spark]
38a0860 [MechCoder] rename pyTreeWeights to javaTreeWeights
6d16ad8 [MechCoder] Fix Python 3 Error
47d7023 [MechCoder] Use np.allclose and treeEnsembleModel -> TreeEnsembleMethods
819098c [MechCoder] [SPARK-8711] [ML] Add additional methods ot PySpark ML tree models

mllib/src/main/scala/org/apache/spark/ml/tree/treeModels.scala

@@ -17,6 +17,7 @@
 
 package org.apache.spark.ml.tree
 
+import org.apache.spark.mllib.linalg.{Vectors, Vector}
 
 /**
  * Abstraction for Decision Tree models.
@@ -70,6 +71,10 @@ private[ml] trait TreeEnsembleModel {
   /** Weights for each tree, zippable with [[trees]] */
   def treeWeights: Array[Double]
 
+  /** Weights used by the python wrappers. */
+  // Note: An array cannot be returned directly due to serialization problems.
+  private[spark] def javaTreeWeights: Vector = Vectors.dense(treeWeights)
+
   /** Summary of the model */
   override def toString: String = {
     // Implementing classes should generally override this method to be more descriptive.

python/pyspark/ml/classification.py

@@ -18,7 +18,8 @@
 from pyspark.ml.util import keyword_only
 from pyspark.ml.wrapper import JavaEstimator, JavaModel
 from pyspark.ml.param.shared import *
-from pyspark.ml.regression import RandomForestParams
+from pyspark.ml.regression import (
+    RandomForestParams, DecisionTreeModel, TreeEnsembleModels)
 from pyspark.mllib.common import inherit_doc
 
 
@@ -202,6 +203,10 @@ class DecisionTreeClassifier(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPred
     >>> td = si_model.transform(df)
     >>> dt = DecisionTreeClassifier(maxDepth=2, labelCol="indexed")
     >>> model = dt.fit(td)
+    >>> model.numNodes
+    3
+    >>> model.depth
+    1
     >>> test0 = sqlContext.createDataFrame([(Vectors.dense(-1.0),)], ["features"])
     >>> model.transform(test0).head().prediction
     0.0
@@ -269,7 +274,8 @@ class DecisionTreeClassifier(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPred
         return self.getOrDefault(self.impurity)
 
 
-class DecisionTreeClassificationModel(JavaModel):
+@inherit_doc
+class DecisionTreeClassificationModel(DecisionTreeModel):
     """
     Model fitted by DecisionTreeClassifier.
     """
@@ -284,6 +290,7 @@ class RandomForestClassifier(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPred
     It supports both binary and multiclass labels, as well as both continuous and categorical
     features.
 
+    >>> from numpy import allclose
     >>> from pyspark.mllib.linalg import Vectors
     >>> from pyspark.ml.feature import StringIndexer
     >>> df = sqlContext.createDataFrame([
@@ -294,6 +301,8 @@ class RandomForestClassifier(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPred
     >>> td = si_model.transform(df)
     >>> rf = RandomForestClassifier(numTrees=2, maxDepth=2, labelCol="indexed", seed=42)
     >>> model = rf.fit(td)
+    >>> allclose(model.treeWeights, [1.0, 1.0])
+    True
     >>> test0 = sqlContext.createDataFrame([(Vectors.dense(-1.0),)], ["features"])
     >>> model.transform(test0).head().prediction
     0.0
@@ -423,7 +432,7 @@ class RandomForestClassifier(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPred
         return self.getOrDefault(self.featureSubsetStrategy)
 
 
-class RandomForestClassificationModel(JavaModel):
+class RandomForestClassificationModel(TreeEnsembleModels):
     """
     Model fitted by RandomForestClassifier.
     """
@@ -438,6 +447,7 @@ class GBTClassifier(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPredictionCol
     It supports binary labels, as well as both continuous and categorical features.
     Note: Multiclass labels are not currently supported.
 
+    >>> from numpy import allclose
     >>> from pyspark.mllib.linalg import Vectors
     >>> from pyspark.ml.feature import StringIndexer
     >>> df = sqlContext.createDataFrame([
@@ -448,6 +458,8 @@ class GBTClassifier(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPredictionCol
     >>> td = si_model.transform(df)
     >>> gbt = GBTClassifier(maxIter=5, maxDepth=2, labelCol="indexed")
     >>> model = gbt.fit(td)
+    >>> allclose(model.treeWeights, [1.0, 0.1, 0.1, 0.1, 0.1])
+    True
     >>> test0 = sqlContext.createDataFrame([(Vectors.dense(-1.0),)], ["features"])
     >>> model.transform(test0).head().prediction
     0.0
@@ -558,7 +570,7 @@ class GBTClassifier(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPredictionCol
         return self.getOrDefault(self.stepSize)
 
 
-class GBTClassificationModel(JavaModel):
+class GBTClassificationModel(TreeEnsembleModels):
     """
     Model fitted by GBTClassifier.
     """

python/pyspark/ml/regression.py

@@ -172,6 +172,10 @@ class DecisionTreeRegressor(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPredi
     ...     (0.0, Vectors.sparse(1, [], []))], ["label", "features"])
     >>> dt = DecisionTreeRegressor(maxDepth=2)
     >>> model = dt.fit(df)
+    >>> model.depth
+    1
+    >>> model.numNodes
+    3
     >>> test0 = sqlContext.createDataFrame([(Vectors.dense(-1.0),)], ["features"])
     >>> model.transform(test0).head().prediction
     0.0
@@ -239,7 +243,37 @@ class DecisionTreeRegressor(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPredi
         return self.getOrDefault(self.impurity)
 
 
-class DecisionTreeRegressionModel(JavaModel):
+@inherit_doc
+class DecisionTreeModel(JavaModel):
+
+    @property
+    def numNodes(self):
+        """Return number of nodes of the decision tree."""
+        return self._call_java("numNodes")
+
+    @property
+    def depth(self):
+        """Return depth of the decision tree."""
+        return self._call_java("depth")
+
+    def __repr__(self):
+        return self._call_java("toString")
+
+
+@inherit_doc
+class TreeEnsembleModels(JavaModel):
+
+    @property
+    def treeWeights(self):
+        """Return the weights for each tree"""
+        return list(self._call_java("javaTreeWeights"))
+
+    def __repr__(self):
+        return self._call_java("toString")
+
+
+@inherit_doc
+class DecisionTreeRegressionModel(DecisionTreeModel):
     """
     Model fitted by DecisionTreeRegressor.
     """
@@ -253,12 +287,15 @@ class RandomForestRegressor(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPredi
     learning algorithm for regression.
     It supports both continuous and categorical features.
 
+    >>> from numpy import allclose
     >>> from pyspark.mllib.linalg import Vectors
     >>> df = sqlContext.createDataFrame([
     ...     (1.0, Vectors.dense(1.0)),
     ...     (0.0, Vectors.sparse(1, [], []))], ["label", "features"])
     >>> rf = RandomForestRegressor(numTrees=2, maxDepth=2, seed=42)
     >>> model = rf.fit(df)
+    >>> allclose(model.treeWeights, [1.0, 1.0])
+    True
     >>> test0 = sqlContext.createDataFrame([(Vectors.dense(-1.0),)], ["features"])
     >>> model.transform(test0).head().prediction
     0.0
@@ -389,7 +426,7 @@ class RandomForestRegressor(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPredi
         return self.getOrDefault(self.featureSubsetStrategy)
 
 
-class RandomForestRegressionModel(JavaModel):
+class RandomForestRegressionModel(TreeEnsembleModels):
     """
     Model fitted by RandomForestRegressor.
     """
@@ -403,12 +440,15 @@ class GBTRegressor(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPredictionCol,
     learning algorithm for regression.
     It supports both continuous and categorical features.
 
+    >>> from numpy import allclose
     >>> from pyspark.mllib.linalg import Vectors
     >>> df = sqlContext.createDataFrame([
     ...     (1.0, Vectors.dense(1.0)),
     ...     (0.0, Vectors.sparse(1, [], []))], ["label", "features"])
     >>> gbt = GBTRegressor(maxIter=5, maxDepth=2)
     >>> model = gbt.fit(df)
+    >>> allclose(model.treeWeights, [1.0, 0.1, 0.1, 0.1, 0.1])
+    True
     >>> test0 = sqlContext.createDataFrame([(Vectors.dense(-1.0),)], ["features"])
     >>> model.transform(test0).head().prediction
     0.0
@@ -518,7 +558,7 @@ class GBTRegressor(JavaEstimator, HasFeaturesCol, HasLabelCol, HasPredictionCol,
         return self.getOrDefault(self.stepSize)
 
 
-class GBTRegressionModel(JavaModel):
+class GBTRegressionModel(TreeEnsembleModels):
     """
     Model fitted by GBTRegressor.
     """