Source code for pyspark.mllib.tree
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from __future__ import absolute_import
import random
from pyspark import SparkContext, RDD
from pyspark.mllib.common import callMLlibFunc, JavaModelWrapper
from pyspark.mllib.linalg import _convert_to_vector
from pyspark.mllib.regression import LabeledPoint
__all__ = ['DecisionTreeModel', 'DecisionTree', 'RandomForestModel', 'RandomForest']
[docs]class DecisionTreeModel(JavaModelWrapper):
"""
A decision tree model for classification or regression.
EXPERIMENTAL: This is an experimental API.
It will probably be modified in future.
"""
[docs] def predict(self, x):
"""
Predict the label of one or more examples.
:param x: Data point (feature vector),
or an RDD of data points (feature vectors).
"""
if isinstance(x, RDD):
return self.call("predict", x.map(_convert_to_vector))
else:
return self.call("predict", _convert_to_vector(x))
def __repr__(self):
""" summary of model. """
return self._java_model.toString()
[docs]class DecisionTree(object):
"""
Learning algorithm for a decision tree model for classification or regression.
EXPERIMENTAL: This is an experimental API.
It will probably be modified in future.
"""
@classmethod
def _train(cls, data, type, numClasses, features, impurity="gini", maxDepth=5, maxBins=32,
minInstancesPerNode=1, minInfoGain=0.0):
first = data.first()
assert isinstance(first, LabeledPoint), "the data should be RDD of LabeledPoint"
model = callMLlibFunc("trainDecisionTreeModel", data, type, numClasses, features,
impurity, maxDepth, maxBins, minInstancesPerNode, minInfoGain)
return DecisionTreeModel(model)
@classmethod
[docs] def trainClassifier(cls, data, numClasses, categoricalFeaturesInfo,
impurity="gini", maxDepth=5, maxBins=32, minInstancesPerNode=1,
minInfoGain=0.0):
"""
Train a DecisionTreeModel for classification.
:param data: Training data: RDD of LabeledPoint.
Labels are integers {0,1,...,numClasses}.
:param numClasses: Number of classes for classification.
:param categoricalFeaturesInfo: Map from categorical feature index
to number of categories.
Any feature not in this map
is treated as continuous.
:param impurity: Supported values: "entropy" or "gini"
:param maxDepth: Max depth of tree.
E.g., depth 0 means 1 leaf node.
Depth 1 means 1 internal node + 2 leaf nodes.
:param maxBins: Number of bins used for finding splits at each node.
:param minInstancesPerNode: Min number of instances required at child
nodes to create the parent split
:param minInfoGain: Min info gain required to create a split
:return: DecisionTreeModel
Example usage:
>>> from numpy import array
>>> from pyspark.mllib.regression import LabeledPoint
>>> from pyspark.mllib.tree import DecisionTree
>>>
>>> data = [
... LabeledPoint(0.0, [0.0]),
... LabeledPoint(1.0, [1.0]),
... LabeledPoint(1.0, [2.0]),
... LabeledPoint(1.0, [3.0])
... ]
>>> model = DecisionTree.trainClassifier(sc.parallelize(data), 2, {})
>>> print model, # it already has newline
DecisionTreeModel classifier of depth 1 with 3 nodes
>>> print model.toDebugString(), # it already has newline
DecisionTreeModel classifier of depth 1 with 3 nodes
If (feature 0 <= 0.0)
Predict: 0.0
Else (feature 0 > 0.0)
Predict: 1.0
>>> model.predict(array([1.0]))
1.0
>>> model.predict(array([0.0]))
0.0
>>> rdd = sc.parallelize([[1.0], [0.0]])
>>> model.predict(rdd).collect()
[1.0, 0.0]
"""
return cls._train(data, "classification", numClasses, categoricalFeaturesInfo,
impurity, maxDepth, maxBins, minInstancesPerNode, minInfoGain)
@classmethod
[docs] def trainRegressor(cls, data, categoricalFeaturesInfo,
impurity="variance", maxDepth=5, maxBins=32, minInstancesPerNode=1,
minInfoGain=0.0):
"""
Train a DecisionTreeModel for regression.
:param data: Training data: RDD of LabeledPoint.
Labels are real numbers.
:param categoricalFeaturesInfo: Map from categorical feature index
to number of categories.
Any feature not in this map
is treated as continuous.
:param impurity: Supported values: "variance"
:param maxDepth: Max depth of tree.
E.g., depth 0 means 1 leaf node.
Depth 1 means 1 internal node + 2 leaf nodes.
:param maxBins: Number of bins used for finding splits at each node.
:param minInstancesPerNode: Min number of instances required at child
nodes to create the parent split
:param minInfoGain: Min info gain required to create a split
:return: DecisionTreeModel
Example usage:
>>> from pyspark.mllib.regression import LabeledPoint
>>> from pyspark.mllib.tree import DecisionTree
>>> from pyspark.mllib.linalg import SparseVector
>>>
>>> sparse_data = [
... LabeledPoint(0.0, SparseVector(2, {0: 0.0})),
... LabeledPoint(1.0, SparseVector(2, {1: 1.0})),
... LabeledPoint(0.0, SparseVector(2, {0: 0.0})),
... LabeledPoint(1.0, SparseVector(2, {1: 2.0}))
... ]
>>>
>>> model = DecisionTree.trainRegressor(sc.parallelize(sparse_data), {})
>>> model.predict(SparseVector(2, {1: 1.0}))
1.0
>>> model.predict(SparseVector(2, {1: 0.0}))
0.0
>>> rdd = sc.parallelize([[0.0, 1.0], [0.0, 0.0]])
>>> model.predict(rdd).collect()
[1.0, 0.0]
"""
return cls._train(data, "regression", 0, categoricalFeaturesInfo,
impurity, maxDepth, maxBins, minInstancesPerNode, minInfoGain)
[docs]class RandomForestModel(JavaModelWrapper):
"""
Represents a random forest model.
EXPERIMENTAL: This is an experimental API.
It will probably be modified in future.
"""
[docs] def predict(self, x):
"""
Predict values for a single data point or an RDD of points using
the model trained.
"""
if isinstance(x, RDD):
return self.call("predict", x.map(_convert_to_vector))
else:
return self.call("predict", _convert_to_vector(x))
[docs] def totalNumNodes(self):
"""
Get total number of nodes, summed over all trees in the forest.
"""
return self.call("totalNumNodes")
def __repr__(self):
""" Summary of model """
return self._java_model.toString()
[docs]class RandomForest(object):
"""
Learning algorithm for a random forest model for classification or regression.
EXPERIMENTAL: This is an experimental API.
It will probably be modified in future.
"""
supportedFeatureSubsetStrategies = ("auto", "all", "sqrt", "log2", "onethird")
@classmethod
def _train(cls, data, algo, numClasses, categoricalFeaturesInfo, numTrees,
featureSubsetStrategy, impurity, maxDepth, maxBins, seed):
first = data.first()
assert isinstance(first, LabeledPoint), "the data should be RDD of LabeledPoint"
if featureSubsetStrategy not in cls.supportedFeatureSubsetStrategies:
raise ValueError("unsupported featureSubsetStrategy: %s" % featureSubsetStrategy)
if seed is None:
seed = random.randint(0, 1 << 30)
model = callMLlibFunc("trainRandomForestModel", data, algo, numClasses,
categoricalFeaturesInfo, numTrees, featureSubsetStrategy, impurity,
maxDepth, maxBins, seed)
return RandomForestModel(model)
@classmethod
[docs] def trainClassifier(cls, data, numClasses, categoricalFeaturesInfo, numTrees,
featureSubsetStrategy="auto", impurity="gini", maxDepth=4, maxBins=32,
seed=None):
"""
Method to train a decision tree model for binary or multiclass
classification.
:param data: Training dataset: RDD of LabeledPoint. Labels should take
values {0, 1, ..., numClasses-1}.
:param numClasses: number of classes for classification.
:param categoricalFeaturesInfo: Map storing arity of categorical features.
E.g., an entry (n -> k) indicates that feature n is categorical
with k categories indexed from 0: {0, 1, ..., k-1}.
:param numTrees: Number of trees in the random forest.
:param featureSubsetStrategy: Number of features to consider for splits at
each node.
Supported: "auto" (default), "all", "sqrt", "log2", "onethird".
If "auto" is set, this parameter is set based on numTrees:
if numTrees == 1, set to "all";
if numTrees > 1 (forest) set to "sqrt".
:param impurity: Criterion used for information gain calculation.
Supported values: "gini" (recommended) or "entropy".
:param maxDepth: Maximum depth of the tree. E.g., depth 0 means 1 leaf node;
depth 1 means 1 internal node + 2 leaf nodes. (default: 4)
:param maxBins: maximum number of bins used for splitting features
(default: 100)
:param seed: Random seed for bootstrapping and choosing feature subsets.
:return: RandomForestModel that can be used for prediction
Example usage:
>>> from pyspark.mllib.regression import LabeledPoint
>>> from pyspark.mllib.tree import RandomForest
>>>
>>> data = [
... LabeledPoint(0.0, [0.0]),
... LabeledPoint(0.0, [1.0]),
... LabeledPoint(1.0, [2.0]),
... LabeledPoint(1.0, [3.0])
... ]
>>> model = RandomForest.trainClassifier(sc.parallelize(data), 2, {}, 3, seed=42)
>>> model.numTrees()
3
>>> model.totalNumNodes()
7
>>> print model,
TreeEnsembleModel classifier with 3 trees
>>> print model.toDebugString(),
TreeEnsembleModel classifier with 3 trees
<BLANKLINE>
Tree 0:
Predict: 1.0
Tree 1:
If (feature 0 <= 1.0)
Predict: 0.0
Else (feature 0 > 1.0)
Predict: 1.0
Tree 2:
If (feature 0 <= 1.0)
Predict: 0.0
Else (feature 0 > 1.0)
Predict: 1.0
>>> model.predict([2.0])
1.0
>>> model.predict([0.0])
0.0
>>> rdd = sc.parallelize([[3.0], [1.0]])
>>> model.predict(rdd).collect()
[1.0, 0.0]
"""
return cls._train(data, "classification", numClasses,
categoricalFeaturesInfo, numTrees, featureSubsetStrategy, impurity,
maxDepth, maxBins, seed)
@classmethod
[docs] def trainRegressor(cls, data, categoricalFeaturesInfo, numTrees, featureSubsetStrategy="auto",
impurity="variance", maxDepth=4, maxBins=32, seed=None):
"""
Method to train a decision tree model for regression.
:param data: Training dataset: RDD of LabeledPoint. Labels are
real numbers.
:param categoricalFeaturesInfo: Map storing arity of categorical
features. E.g., an entry (n -> k) indicates that feature
n is categorical with k categories indexed from 0:
{0, 1, ..., k-1}.
:param numTrees: Number of trees in the random forest.
:param featureSubsetStrategy: Number of features to consider for
splits at each node.
Supported: "auto" (default), "all", "sqrt", "log2", "onethird".
If "auto" is set, this parameter is set based on numTrees:
if numTrees == 1, set to "all";
if numTrees > 1 (forest) set to "onethird" for regression.
:param impurity: Criterion used for information gain calculation.
Supported values: "variance".
:param maxDepth: Maximum depth of the tree. E.g., depth 0 means 1
leaf node; depth 1 means 1 internal node + 2 leaf nodes.
(default: 4)
:param maxBins: maximum number of bins used for splitting features
(default: 100)
:param seed: Random seed for bootstrapping and choosing feature subsets.
:return: RandomForestModel that can be used for prediction
Example usage:
>>> from pyspark.mllib.regression import LabeledPoint
>>> from pyspark.mllib.tree import RandomForest
>>> from pyspark.mllib.linalg import SparseVector
>>>
>>> sparse_data = [
... LabeledPoint(0.0, SparseVector(2, {0: 1.0})),
... LabeledPoint(1.0, SparseVector(2, {1: 1.0})),
... LabeledPoint(0.0, SparseVector(2, {0: 1.0})),
... LabeledPoint(1.0, SparseVector(2, {1: 2.0}))
... ]
>>>
>>> model = RandomForest.trainRegressor(sc.parallelize(sparse_data), {}, 2, seed=42)
>>> model.numTrees()
2
>>> model.totalNumNodes()
4
>>> model.predict(SparseVector(2, {1: 1.0}))
1.0
>>> model.predict(SparseVector(2, {0: 1.0}))
0.5
>>> rdd = sc.parallelize([[0.0, 1.0], [1.0, 0.0]])
>>> model.predict(rdd).collect()
[1.0, 0.5]
"""
return cls._train(data, "regression", 0, categoricalFeaturesInfo, numTrees,
featureSubsetStrategy, impurity, maxDepth, maxBins, seed)
def _test():
import doctest
globs = globals().copy()
globs['sc'] = SparkContext('local[4]', 'PythonTest', batchSize=2)
(failure_count, test_count) = doctest.testmod(globs=globs, optionflags=doctest.ELLIPSIS)
globs['sc'].stop()
if failure_count:
exit(-1)
if __name__ == "__main__":
_test()
