Source Code for Module pypower.fairmax

 1  # Copyright (C) 1996-2011 Power System Engineering Research Center (PSERC) 
 2  # Copyright (C) 2011 Richard Lincoln 
 3  # 
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16   
17  """Same as built-in C{max}, except breaks ties randomly. 
18  """ 
19   
20  from random import random 
21  from numpy import nonzero, fix 
22   
23   
24 -def fairmax(x): 
25      """Same as built-in C{max}, except breaks ties randomly. 
26   
27      Takes a vector as an argument and returns the same output as the 
28      built-in function C{max} with two output parameters, except that 
29      where the maximum value occurs at more than one position in the 
30      vector, the index is chosen randomly from these positions as opposed 
31      to just choosing the first occurance. 
32   
33      @see: C{max} 
34   
35      @author: Ray Zimmerman (PSERC Cornell) 
36      @author: Richard Lincoln 
37      """ 
38      val = max(x)                      ## find max value 
39      i   = nonzero(x == val)           ## find all positions where this occurs 
40      n   = len(i)                      ## number of occurences 
41      idx = i( fix(n * random()) + 1 )  ## select index randomly among occurances 
42   
43      return val, idx 
44