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Source Code for Module fuzzy.Rule

  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  """Represents a fuzzy rule.""" 
 19  __revision__ = "$Id: Rule.py,v 1.17 2010-02-17 19:57:13 rliebscher Exp $" 
 20   
 21  from fuzzy.norm.Min import Min 
 22   
 23 -class Rule(object): 
 24      """This is realizes an important part of the inference engine. 
 25         It represents and calculates the value of a fuzzy rule 
 26         and sets the given adjective to the appropriate value. 
 27   
 28         @cvar _CER: the default value (=Min()) for the norm used to calculate the certainty of a rule. 
 29         @type _CER: L{fuzzy.norm.Norm.Norm} 
 30         @ivar adjective: fuzzy adjective to set 
 31         @type adjective: L{fuzzy.Adjective.Adjective} 
 32         @ivar operator: Operator which provides the value to set 
 33         @type operator: L{fuzzy.operator.Operator.Operator} 
 34         @ivar certainty: how sure are we about this rule 
 35         @type certainty: float 
 36         @ivar CER: fuzzy norm to use with certainty (normally a t-norm) 
 37         @type CER: L{fuzzy.norm.Norm.Norm} 
 38      """ 
 39   
 40      # default if not set in instance 
 41      _CER = Min() 
 42   
 43 -    def __init__(self, adjective, operator, certainty=1.0, CER=None): 
 44          """Initialize instance. 
 45             @param adjective: fuzzy adjective to set 
 46             @type adjective: L{fuzzy.Adjective.Adjective} 
 47             @param operator: Operator which provides the value to set 
 48             @type operator: L{fuzzy.operator.Operator.Operator} 
 49             @param certainty: how sure are we about this rule 
 50             @type certainty: float 
 51             @param CER: fuzzy norm to use with certainty (normally a t-norm) 
 52             @type CER: L{fuzzy.norm.Norm.Norm} 
 53          """ 
 54   
 55          self.adjective = adjective 
 56          self.operator = operator 
 57          self.certainty = certainty 
 58          self.CER = CER 
 59   
 60 -    def compute(self): 
 61          """Compute and set value for given fuzzy adjective.""" 
 62   
 63          import fuzzy.Adjective 
 64          if isinstance(self.adjective, fuzzy.Adjective.Adjective): 
 65              self.adjective.setMembership( 
 66                                      (self.CER or self._CER)( 
 67                                          self.certainty,       # how sure are we about this rule 
 68                                          self.operator() # value from input 
 69                                      ) 
 70                                  ) 
 71          elif isinstance(self.adjective, list): 
 72              for adj in self.adjective: 
 73                  adj.setMembership( 
 74                                      (self.CER or self._CER)( 
 75                                          self.certainty,       # how sure are we about this rule 
 76                                          self.operator() # value from input 
 77                                      ) 
 78                                  ) 
 79          else: 
 80              from fuzzy.Exception import FuzzyException 
 81              raise FuzzyException("rule target not set.") 
 82   
 83 -    def getName(self, system): 
 84          """Lookup the name given this rule in the given system""" 
 85          return system.findRuleName(self) 
 86   
 87 -    def __repr__(self): 
 88          """Return representation of instance. 
 89                      
 90             @return: representation of instance 
 91             @rtype: string 
 92             """ 
 93          params = [] 
 94          params.append("adjective=%s" % object.__repr__(self.adjective)) 
 95          params.append("operator=%s" % repr(self.operator)) 
 96          if self.certainty != 1.0: params.append("certainty=%s" % self.certainty) 
 97          if self.CER: params.append("CER=%s" % repr(self.CER)) 
 98          return "%s.%s(%s)" % (self.__class__.__module__, self.__class__.__name__, ", ".join(params)) 
 99   

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