# Source code for pyFTS.partitioners.Huarng

    """
    K. H. Huarng, “Effective lengths of intervals to improve forecasting in fuzzy time series,”
    Fuzzy Sets Syst., vol. 123, no. 3, pp. 387–394, Nov. 2001.
    """

    import numpy as np
    import math
    import random as rnd
    import functools, operator
    from pyFTS.common import FuzzySet, Membership, Transformations

    from pyFTS.partitioners import partitioner

    class HuarngPartitioner(partitioner.Partitioner):
        """Huarng Empirical Partitioner"""
        def __init__(self, **kwargs):
            super(HuarngPartitioner, self).__init__(name="Huarng", **kwargs)

        def build(self, data):
            diff = Transformations.Differential(1)
            data2 = diff.apply(data)
            davg = np.abs( np.mean(data2) / 2 )

            if davg <= 1.0:
                base = 0.1
            elif 1 < davg <= 10:
                base = 1.0
            elif 10 < davg <= 100:
                base = 10
            else:
                base = 100

            sets = {}

            dlen = self.max - self.min
            npart = math.ceil(dlen / base)
            partition = math.ceil(self.min)
            for c in range(npart):
                _name = self.get_name(c)
                if self.membership_function == Membership.trimf:
                    sets[_name] = FuzzySet.FuzzySet(_name, Membership.trimf,
                                                   [partition - base, partition, partition + base], partition)
                elif self.membership_function == Membership.gaussmf:
                    sets[_name] = FuzzySet.FuzzySet(_name, Membership.gaussmf,
                                                  [partition, base/2], partition)
                elif self.membership_function == Membership.trapmf:
                    sets[_name] = FuzzySet.FuzzySet(_name, Membership.trapmf,
                                                  [partition - base, partition - (base/2),
                                                   partition + (base / 2), partition + base], partition)

                partition += base

            return sets