106 lines
3.3 KiB
Python
106 lines
3.3 KiB
Python
import numpy as np
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import math
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import random as rnd
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import functools, operator
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from pyFTS.common import FuzzySet, Membership
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from pyFTS.partitioners import partitioner
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# C. H. Cheng, R. J. Chang, and C. A. Yeh, “Entropy-based and trapezoidal fuzzification-based fuzzy time series approach for forecasting IT project cost,”
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# Technol. Forecast. Social Change, vol. 73, no. 5, pp. 524–542, Jun. 2006.
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def splitBelow(data,threshold):
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return [k for k in data if k <= threshold]
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def splitAbove(data,threshold):
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return [k for k in data if k > threshold]
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def PMF(data, threshold):
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a = sum([1.0 for k in splitBelow(data,threshold)])
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b = sum([1.0 for k in splitAbove(data, threshold)])
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l = len(data)
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return [a / l, b / l]
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def entropy(data, threshold):
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pmf = PMF(data, threshold)
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if pmf[0] == 0 or pmf[1] == 0:
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return 1
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else:
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return - sum([pmf[0] * math.log(pmf[0]), pmf[1] * math.log(pmf[1])])
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def informationGain(data, thres1, thres2):
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return entropy(data, thres1) - entropy(data, thres2)
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def bestSplit(data, npart):
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if len(data) < 2:
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return None
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count = 1
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ndata = list(set(data))
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ndata.sort()
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l = len(ndata)
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threshold = 0
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try:
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while count < l and informationGain(data, ndata[count - 1], ndata[count]) <= 0:
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threshold = ndata[count]
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count += 1
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except IndexError:
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print(threshold)
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print (ndata)
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print (count)
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rem = npart % 2
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if (npart - rem)/2 > 1:
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p1 = splitBelow(data,threshold)
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p2 = splitAbove(data,threshold)
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if len(p1) > len(p2):
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np1 = (npart - rem)/2 + rem
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np2 = (npart - rem)/2
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else:
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np1 = (npart - rem) / 2
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np2 = (npart - rem) / 2 + rem
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tmp = [threshold]
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for k in bestSplit(p1, np1 ): tmp.append(k)
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for k in bestSplit(p2, np2 ): tmp.append(k)
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return tmp
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else:
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return [threshold]
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class EntropyPartitioner(partitioner.Partitioner):
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"""Huarng Entropy Partitioner"""
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def __init__(self, data, npart, func = Membership.trimf, transformation=None, indexer=None):
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super(EntropyPartitioner, self).__init__("Entropy", data, npart, func=func, transformation=transformation, indexer=indexer)
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def build(self, data):
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sets = []
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partitions = bestSplit(data, self.partitions)
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partitions.append(self.min)
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partitions.append(self.max)
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partitions = list(set(partitions))
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partitions.sort()
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for c in np.arange(1, len(partitions) - 1):
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if self.membership_function == Membership.trimf:
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sets.append(FuzzySet.FuzzySet(self.prefix + str(c), Membership.trimf,
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[partitions[c - 1], partitions[c], partitions[c + 1]],partitions[c]))
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elif self.membership_function == Membership.trapmf:
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b1 = (partitions[c] - partitions[c - 1])/2
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b2 = (partitions[c + 1] - partitions[c]) / 2
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sets.append(FuzzySet.FuzzySet(self.prefix + str(c), Membership.trapmf,
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[partitions[c - 1], partitions[c] - b1,
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partitions[c] + b2, partitions[c + 1]],
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partitions[c]))
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return sets
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