[EM] Re: Condorcet package-wvx

[Dave Ketchum]

On Fri, 25 Feb 2005 03:32:29 -0600 Daniel Bishop wrote:

> Dave Ketchum wrote:
> 
>> On Fri, 25 Feb 2005 00:01:11 -0800 Russ Paielli wrote:
>>
>> ...
>>
>>> On the theoretical side, what exactly would an equal-ranking 
>>> capability accomplish? Does it give the voter some significant 
>>> strategic mechanism, or is it simply way for the voter to express 
>>> indecision? If it's the latter, then it is completely unnecessary. If 
>>> the voter truly rates the candidates as precisely equal down to the 
>>> tenth decimal place, then it really shouldn't matter to him which he 
>>> ranks above the other. If the decision is really that difficult, he 
>>> can flip a coin. Why make the system more complicated than it needs 
>>> to be?
>>
>>
>>
>> Conceded it complicates the counting, though I do not see that as major.
> 
> 
> It doesn't complicate the counting.  Especially if you use the code from 
> my website.
> 
> def pairwise_matrix(ballots):
>   """Return a matrix M such that M[i][j] = votes for candidate #i over #j.
> 
>   ballots = a list of ballots, where each ballot is a list B with each
>             B[i] = the rank (1=best) of candidate #i"""
>   if not ballots:
>      return []
>   n = len(ballots[0]) # number of candidates
>   matrix = [[0] * n for i in xrange(n)]
>   for ballot in ballots:
>      if len(ballot) != n:
>         raise ValueError("ballots have unequal lengths")
>      for i in xrange(n):
>         for j in xrange(n):
>            if ballot[i] < ballot[j]: # i preferred over j
>               matrix[i][j] += 1
> 
> Note that there's not even an explicit test for equal rankings.
> 
> (The GUI is simply a row of radio buttons for each candidate, each 
> corresponding to a rank,)


BUT - wvx wants to count =, so redoing your last 3 lines - I think in same 
syntax (I assume a large number (blank) for unranked candidates - I get 
rid of pairs you do not care about, and I want to avoid, early):

          for j in xrange(n):
             if i != j: # avoiding the diagonal
                if ballot[i] != blank: # avoiding unranked candidates
                   if ballot[i] < ballot[j]: # i preferred over j
                      matrix[i][j] += 2 # numbers doubled to avoid .5
                   if ballot[i] = ballot[j]: # ranked equal
                      matrix[i][j] += 1
-- 
  davek at clarityconnect.com    people.clarityconnect.com/webpages3/davek
  Dave Ketchum   108 Halstead Ave, Owego, NY  13827-1708   607-687-5026
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