- Non Stationary Fuzzy Sets

pyFTS/common/FuzzySet.py

@@ -3,7 +3,7 @@ from pyFTS import *
 from pyFTS.common import Membership
 
 
-class FuzzySet:
+class FuzzySet(object):
     """
     Fuzzy Set
     """

pyFTS/common/Membership.py

@@ -1,3 +1,7 @@
+"""
+Membership functions for Fuzzy Sets
+"""
+
 import numpy as np
 import math
 from pyFTS import *

pyFTS/common/NonStationary.py

@@ -0,0 +1,38 @@
+import numpy as np
+from pyFTS import *
+from pyFTS.common import FuzzySet, Membership
+
+
+class NonStationaryFuzzySet(FuzzySet.FuzzySet):
+    """
+    Non Stationary Fuzzy Sets
+
+    GARIBALDI, Jonathan M.; JAROSZEWSKI, Marcin; MUSIKASUWAN, Salang. Nonstationary fuzzy sets.
+    IEEE Transactions on Fuzzy Systems, v. 16, n. 4, p. 1072-1086, 2008.
+    """
+
+    def __init__(self, name, mf, parameters):
+        """
+        Constructor
+        :param name: Fuzzy Set name
+        :param mf: Membership Function
+        :param pf: Pertubation Function
+        :param parameters: initial parameters of the membership function
+        :param pf_parameters: parameters of the membership pertubation function
+        """
+        super(FuzzySet, self).__init__(order=1, name=name, **kwargs)
+        self.name = name
+        self.mf = mf
+        self.parameters = parameters
+        self.pf = []
+        self.pf_parameters = []
+
+    def appendPertubation(self, pf, pf_parameters):
+        """
+        Append a pertubation function to the non-stationary fuzzy set
+        :param pf:
+        :param pf_parameters:
+        :return:
+        """
+        self.pf.append(pf)
+        self.pf_parameters.append(pf_parameters)

pyFTS/common/Pertubation.py

@@ -0,0 +1,27 @@
+"""
+Pertubation functions for Non Stationary Fuzzy Sets
+"""
+
+import numpy as np
+from pyFTS import *
+from pyFTS.common import FuzzySet, Membership
+
+
+def linear(x, parameters):
+    return parameters[0]*x + parameters[1]
+
+
+def polynomial(x, parameters):
+    n = len(parameters)
+    tmp = 0.0
+    for k in np.arange(0,n):
+        tmp += parameters[k] * x**k
+    return tmp
+
+
+def exponential(x, parameters):
+    return np.exp(x*parameters[0])
+
+
+def periodic(x, parameters):
+    return np.sin(x * parameters[0] + parameters[1])

pyFTS/ifts.py

@@ -7,7 +7,12 @@ from pyFTS import hofts, fts, tree
 
 
 class IntervalFTS(hofts.HighOrderFTS):
-    """High Order Interval Fuzzy Time Series"""
+    """
+    High Order Interval Fuzzy Time Series
+
+    SILVA, Petrônio CL; SADAEI, Hossein Javedani; GUIMARÃES, Frederico Gadelha. Interval Forecasting with Fuzzy Time Series.
+    In: Computational Intelligence (SSCI), 2016 IEEE Symposium Series on. IEEE, 2016. p. 1-8.
+    """
     def __init__(self, name, **kwargs):
         super(IntervalFTS, self).__init__(name="IFTS " + name, **kwargs)
         self.shortname = "IFTS " + name