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Membership.py
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Membership.py
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"""
Membership functions for Fuzzy Sets
"""
import numpy as np
import math
from pyFTS import *
def trimf(x, parameters):
"""
Triangular fuzzy membership function
:param x: data point
:param parameters: a list with 3 real values
:return: the membership value of x given the parameters
"""
xx = np.round(x, 3)
if xx < parameters[0]:
return 0
elif parameters[0] <= xx < parameters[1]:
return (x - parameters[0]) / (parameters[1] - parameters[0])
elif parameters[1] <= xx <= parameters[2]:
return (parameters[2] - xx) / (parameters[2] - parameters[1])
else:
return 0
def trapmf(x, parameters):
"""
Trapezoidal fuzzy membership function
:param x: data point
:param parameters: a list with 4 real values
:return: the membership value of x given the parameters
"""
if x < parameters[0]:
return 0
elif parameters[0] <= x < parameters[1]:
return (x - parameters[0]) / (parameters[1] - parameters[0])
elif parameters[1] <= x <= parameters[2]:
return 1
elif parameters[2] <= x <= parameters[3]:
return (parameters[3] - x) / (parameters[3] - parameters[2])
else:
return 0
def gaussmf(x, parameters):
"""
Gaussian fuzzy membership function
:param x: data point
:param parameters: a list with 2 real values (mean and variance)
:return: the membership value of x given the parameters
"""
return math.exp((-(x - parameters[0])**2)/(2 * parameters[1]**2))
def bellmf(x, parameters):
"""
Bell shaped membership function
:param x:
:param parameters:
:return:
"""
return 1 / (1 + abs((x - parameters[2]) / parameters[0]) ** (2 * parameters[1]))
def sigmf(x, parameters):
"""
Sigmoid / Logistic membership function
:param x:
:param parameters: an list with 2 real values (smoothness and midpoint)
:return
"""
return 1 / (1 + math.exp(-parameters[0] * (x - parameters[1])))
def singleton(x, parameters):
"""
Singleton membership function, a single value fuzzy function
:param x:
:param parameters: a list with one real value
:returns
"""
return 1 if x == parameters[0] else 0