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Source Code for Module fuzzy.set.PiFunction

  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  """Realize a Pi-shaped fuzzy set""" 
 20   
 21  __revision__ = "$Id: PiFunction.py,v 1.19 2010-03-28 18:44:46 rliebscher Exp $" 
 22   
 23   
 24  from fuzzy.set.Function import Function 
 25  from fuzzy.set.SFunction import SFunction 
 26  from fuzzy.set.ZFunction import ZFunction 
 27   
 28 -class PiFunction(Function): 
 29      r""" 
 30      Realize a Pi-shaped fuzzy set:: 
 31           
 32                  _ 
 33                 /|\ 
 34                / | \ 
 35              _/  |  \_ 
 36               |  a  | 
 37               |     | 
 38                delta 
 39   
 40      See also U{http://pyfuzzy.sourceforge.net/demo/set/PiFunction.png} 
 41   
 42       
 43      @ivar a: center of set. 
 44      @type a: float 
 45      @ivar delta: absolute distance between x-values for minimum and maximum. 
 46      @type delta: float 
 47      """ 
 48   
 49 -    def __init__(self, a=0.0, delta=1.0): 
 50          """Initialize a Pi-shaped fuzzy set. 
 51   
 52          @param a: center of set 
 53          @type a: float 
 54          @param delta: absolute distance between x-values for minimum and maximum 
 55          @type delta: float 
 56          """ 
 57          super(PiFunction, self).__init__() 
 58          self.a = a 
 59          self.delta = delta 
 60          self._sfunction = SFunction(a - delta/2., delta/2) 
 61          self._zfunction = ZFunction(a + delta/2., delta/2) 
 62   
 63 -    def __call__(self, x): 
 64          """Return membership of x in this fuzzy set. 
 65             This method makes the set work like a function. 
 66              
 67             @param x: value for which the membership is to calculate 
 68             @type x: float 
 69             @return: membership 
 70             @rtype: float 
 71             """ 
 72          if x < self.a: 
 73              return self._sfunction(x) 
 74          else: 
 75              return self._zfunction(x) 
 76   
 77 -    def getCOG(self): 
 78          """Return center of gravity.""" 
 79          return self.a 
 80   
 81 -    def getValuesX(self): 
 82          """Return sequence of x-values so we get a smooth function.""" 
 83          for x in self._sfunction.getValuesX(): 
 84              yield x 
 85          # first value is equal the last of the previous sequence     
 86          skippedFirst = False  
 87          for x in self._zfunction.getValuesX(): 
 88              if not skippedFirst: 
 89                  skippedFirst = True 
 90              else: 
 91                  yield x 
 92   
 93 -    def __repr__(self): 
 94          """Return representation of instance. 
 95                      
 96             @return: representation of instance 
 97             @rtype: string 
 98             """ 
 99          return "%s.%s(a=%s, delta=%s)" % (self.__class__.__module__, self.__class__.__name__, self.a, self.delta) 
100   

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