python/pyspark/mllib/stat/KernelDensity.py

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#    http://www.apache.org/licenses/LICENSE-2.0
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from typing import Iterable, Optional

import numpy as np
from numpy import ndarray

from pyspark.mllib.common import callMLlibFunc
from pyspark.core.rdd import RDD


class KernelDensity:
    """
    Estimate probability density at required points given an RDD of samples
    from the population.

    Examples
    --------
    >>> kd = KernelDensity()
    >>> sample = sc.parallelize([0.0, 1.0])
    >>> kd.setSample(sample)
    >>> kd.estimate([0.0, 1.0])
    array([ 0.12938758,  0.12938758])
    """

    def __init__(self) -> None:
        self._bandwidth: float = 1.0
        self._sample: Optional[RDD[float]] = None

    def setBandwidth(self, bandwidth: float) -> None:
        """Set bandwidth of each sample. Defaults to 1.0"""
        self._bandwidth = bandwidth

    def setSample(self, sample: RDD[float]) -> None:
        """Set sample points from the population. Should be a RDD"""
        if not isinstance(sample, RDD):
            raise TypeError("samples should be a RDD, received %s" % type(sample))
        self._sample = sample

    def estimate(self, points: Iterable[float]) -> ndarray:
        """Estimate the probability density at points"""
        points = list(points)
        densities = callMLlibFunc("estimateKernelDensity", self._sample, self._bandwidth, points)
        return np.asarray(densities)