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Source Code for Module fuzzy.defuzzify.COGS

 1  # -*- coding: utf-8 -*- 
 2  # 
 3  # Copyright (C) 2009  Rene Liebscher 
 4  # 
 5  # This program is free software; you can redistribute it and/or modify it under 
 6  # the terms of the GNU Lesser General Public License as published by the Free  
 7  # Software Foundation; either version 3 of the License, or (at your option) any 
 8  # later version. 
 9  # 
10  # This program is distributed in the hope that it will be useful, but WITHOUT  
11  # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 
12  # FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more 
13  # details. 
14  #  
15  # You should have received a copy of the GNU Lesser General Public License 
16  # along with this program; if not, see <http://www.gnu.org/licenses/>.  
17  # 
18   
19  """Defuzzification for singletons.""" 
20   
21  __revision__ = "$Id: COGS.py,v 1.8 2010-03-28 18:40:33 rliebscher Exp $" 
22   
23  from fuzzy.defuzzify.Base import Base, DefuzzificationException 
24  import fuzzy.set.Singleton 
25   
26 -class COGS(Base): 
27      """Defuzzification for singletons.""" 
28   
29 -    def __init__(self, INF=None, ACC=None, failsafe=None, *args, **keywords): 
30          """ 
31              @param failsafe: if is not possible to calculate a center of gravity, 
32              return this value if not None or forward the exception 
33          """ 
34          super(COGS, self).__init__(INF, ACC, *args, **keywords) 
35          self.failsafe = failsafe # which value if COG not calculable 
36   
37 -    def getValue(self, variable): 
38          """Defuzzification using center of gravity method.""" 
39          sum_1, sum_2 = 0.,0. 
40          for adjective in variable.adjectives.values(): 
41              # get precomputed adjective set 
42              set = adjective.set 
43              if not isinstance(set, fuzzy.set.Singleton.Singleton): 
44                  raise DefuzzificationException("Only Singleton for COGS defuzzification allowed.") 
45              a = (self.INF or self._INF)(set(set.x), adjective.getMembership()) 
46              sum_1 += set.x*a 
47              sum_2 += a 
48          try: 
49              if sum_2 == 0.: 
50                  raise DefuzzificationException("No result, all singletons set to 0.") 
51              return sum_1/sum_2 
52          except: 
53              # was not to calculate 
54              if self.failsafe is not None: 
55                  # user gave us a value to return 
56                  return self.failsafe 
57              else: 
58                  # forward exception 
59                  raise 
60   
61 -    def _repr_params(self, params): 
62          """Helper for representation of instance. 
63           
64          Add all own params to given list in params.     
65          """ 
66          super(COGS, self)._repr_params(params) 
67          if self.failsafe: params.append("failsafe=%s" % self.failsafe) 
68   

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