pyFTS/partitioners/Huarng.py

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


# 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.
from pyFTS.partitioners import partitioner


class HuarngPartitioner(partitioner.Partitioner):
    def __init__(self, npart,data,func = Membership.trimf):
        super(HuarngPartitioner, self).__init__("Huarng",data,npart,func)

    def build(self, data):
        data2 = Transformations.differential(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 = []
        dmax = max(data)
        dmax += dmax * 0.10
        dmin = min(data)
        dmin -= dmin * 0.10
        dlen = dmax - dmin
        npart = math.ceil(dlen / base)
        partition = math.ceil(dmin)
        for c in range(npart):
            sets.append(
                FuzzySet.FuzzySet(self.prefix + str(c), Membership.trimf, [partition - base, partition, partition + base], partition))
            partition += base

        return sets