#
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# The ASF licenses this file to You under the Apache License, Version 2.0
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#    http://www.apache.org/licenses/LICENSE-2.0
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"""
Logistic regression using MLlib.

This example requires NumPy (http://www.numpy.org/).
"""

from math import exp
import sys

import numpy as np
from pyspark import SparkContext
from pyspark.mllib.regression import LabeledPoint
from pyspark.mllib.classification import LogisticRegressionWithSGD


def parsePoint(line):
    """
    Parse a line of text into an MLlib LabeledPoint object.
    """
    values = [float(s) for s in line.split(' ')]
    if values[0] == -1:   # Convert -1 labels to 0 for MLlib
        values[0] = 0
    return LabeledPoint(values[0], values[1:])


if __name__ == "__main__":
    if len(sys.argv) != 3:
        print >> sys.stderr, "Usage: logistic_regression <file> <iterations>"
        exit(-1)
    sc = SparkContext(appName="PythonLR")
    points = sc.textFile(sys.argv[1]).map(parsePoint)
    iterations = int(sys.argv[2])
    model = LogisticRegressionWithSGD.train(points, iterations)
    print "Final weights: " + str(model.weights)
    print "Final intercept: " + str(model.intercept)
    sc.stop()
