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#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
import numpy
from numpy import array, dot, shape
from pyspark import SparkContext
from pyspark.mllib._common import \
_get_unmangled_rdd, _get_unmangled_double_vector_rdd, \
_serialize_double_matrix, _deserialize_double_matrix, \
_serialize_double_vector, _deserialize_double_vector, \
_get_initial_weights, _serialize_rating, _regression_train_wrapper, \
LinearModel, _linear_predictor_typecheck
from math import exp, log
class LogisticRegressionModel(LinearModel):
"""A linear binary classification model derived from logistic regression.
>>> data = array([0.0, 0.0, 1.0, 1.0, 1.0, 2.0, 1.0, 3.0]).reshape(4,2)
>>> lrm = LogisticRegressionWithSGD.train(sc.parallelize(data))
>>> lrm.predict(array([1.0])) > 0
True
"""
def predict(self, x):
_linear_predictor_typecheck(x, self._coeff)
margin = dot(x, self._coeff) + self._intercept
prob = 1/(1 + exp(-margin))
return 1 if prob > 0.5 else 0
class LogisticRegressionWithSGD(object):
@classmethod
def train(cls, data, iterations=100, step=1.0,
miniBatchFraction=1.0, initialWeights=None):
"""Train a logistic regression model on the given data."""
sc = data.context
return _regression_train_wrapper(sc, lambda d, i:
sc._jvm.PythonMLLibAPI().trainLogisticRegressionModelWithSGD(d._jrdd,
iterations, step, miniBatchFraction, i),
LogisticRegressionModel, data, initialWeights)
class SVMModel(LinearModel):
"""A support vector machine.
>>> data = array([0.0, 0.0, 1.0, 1.0, 1.0, 2.0, 1.0, 3.0]).reshape(4,2)
>>> svm = SVMWithSGD.train(sc.parallelize(data))
>>> svm.predict(array([1.0])) > 0
True
"""
def predict(self, x):
_linear_predictor_typecheck(x, self._coeff)
margin = dot(x, self._coeff) + self._intercept
return 1 if margin >= 0 else 0
class SVMWithSGD(object):
@classmethod
def train(cls, data, iterations=100, step=1.0, regParam=1.0,
miniBatchFraction=1.0, initialWeights=None):
"""Train a support vector machine on the given data."""
sc = data.context
return _regression_train_wrapper(sc, lambda d, i:
sc._jvm.PythonMLLibAPI().trainSVMModelWithSGD(d._jrdd,
iterations, step, regParam, miniBatchFraction, i),
SVMModel, data, initialWeights)
class NaiveBayesModel(object):
"""
Model for Naive Bayes classifiers.
Contains two parameters:
- pi: vector of logs of class priors (dimension C)
- theta: matrix of logs of class conditional probabilities (CxD)
>>> data = array([0.0, 0.0, 1.0, 0.0, 0.0, 2.0, 1.0, 1.0, 0.0]).reshape(3,3)
>>> model = NaiveBayes.train(sc.parallelize(data))
>>> model.predict(array([0.0, 1.0]))
0
>>> model.predict(array([1.0, 0.0]))
1
"""
def __init__(self, pi, theta):
self.pi = pi
self.theta = theta
def predict(self, x):
"""Return the most likely class for a data vector x"""
return numpy.argmax(self.pi + dot(x, self.theta))
class NaiveBayes(object):
@classmethod
def train(cls, data, lambda_=1.0):
"""
Train a Naive Bayes model given an RDD of (label, features) vectors.
This is the Multinomial NB (U{http://tinyurl.com/lsdw6p}) which can
handle all kinds of discrete data. For example, by converting
documents into TF-IDF vectors, it can be used for document
classification. By making every vector a 0-1 vector, it can also be
used as Bernoulli NB (U{http://tinyurl.com/p7c96j6}).
@param data: RDD of NumPy vectors, one per element, where the first
coordinate is the label and the rest is the feature vector
(e.g. a count vector).
@param lambda_: The smoothing parameter
"""
sc = data.context
dataBytes = _get_unmangled_double_vector_rdd(data)
ans = sc._jvm.PythonMLLibAPI().trainNaiveBayes(dataBytes._jrdd, lambda_)
return NaiveBayesModel(
_deserialize_double_vector(ans[0]),
_deserialize_double_matrix(ans[1]))
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()
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