/// <summary>
/// Fills the pairwise preferences.
/// This goes through each voter's ranking options and updates an array indicating
/// which options are preferred over which other options. Each higher-ranked
/// option gains one point in 'beating' a lower-ranked option.
/// </summary>
/// <param name="voterRankings">The voter rankings.</param>
/// <param name="listOfChoices">The list of choices.</param>
/// <returns>Returns a filled-in preferences array.</returns>
private int[,] GetPairwisePreferences(IEnumerable<VoterRankings> voterRankings, List<string> listOfChoices)
{
int[,] pairwisePreferences = new int[listOfChoices.Count, listOfChoices.Count];
var choiceIndexes = GroupRankVotes.GetChoicesIndexes(listOfChoices);
foreach (var voter in voterRankings)
{
var rankedChoices = voter.RankedVotes.Select(v => v.Vote);
var unrankedChoices = listOfChoices.Except(rankedChoices);
foreach (var choice in voter.RankedVotes)
{
// Each choice matching or beating the ranks of other ranked choices is marked.
foreach (var otherChoice in voter.RankedVotes)
{
if ((choice.Vote != otherChoice.Vote) && (choice.Rank <= otherChoice.Rank))
{
pairwisePreferences[choiceIndexes[choice.Vote], choiceIndexes[otherChoice.Vote]]++;
}
}
// Each choice is ranked higher than all unranked choices
foreach (var nonChoice in unrankedChoices)
{
pairwisePreferences[choiceIndexes[choice.Vote], choiceIndexes[nonChoice]]++;
}
}
}
return pairwisePreferences;
}
/// <summary>
/// Fills the pairwise preferences.
/// This goes through each voter's ranking options and updates an array indicating
/// which options are preferred over which other options.
/// Each higher-ranked option gains the difference in ranking in 'beating' a lower-ranked option.
/// </summary>
/// <param name="voterRankings">The voter rankings.</param>
/// <param name="listOfChoices">The list of choices.</param>
/// <returns>Returns a filled-in preferences array.</returns>
private static DistanceData GetPairwiseData(IEnumerable <VoterRankings> voterRankings, List <string> listOfChoices)
{
DistanceData data = new DistanceData
{
Paths = new int[listOfChoices.Count, listOfChoices.Count]
};
var choiceIndexes = GroupRankVotes.GetChoicesIndexes(listOfChoices);
foreach (var voter in voterRankings)
{
var rankedChoices = voter.RankedVotes.Select(v => v.Vote);
var unrankedChoices = listOfChoices.Except(rankedChoices);
foreach (var choice in voter.RankedVotes)
{
foreach (var otherChoice in voter.RankedVotes)
{
// Each ranked vote that has a higher rank (lower number) than each
// alternative has the distance between the choices added to the
// corresponding table entry.
if (choice.Vote != otherChoice.Vote && choice.Rank < otherChoice.Rank)
{
data.Paths[choiceIndexes[choice.Vote], choiceIndexes[otherChoice.Vote]] += otherChoice.Rank - choice.Rank;
}
}
// All unranked options are considered to be at distance 0 from *all* ranked options.
// There is no relative preference, nor does it place unranked options 'beneath'
// ranked options, such that higher ranked options have greater distance from them.
// Unranked options are agnostic choices.
//foreach (var nonChoice in unrankedChoices)
//{
// //data.Paths[choiceIndexes[choice.Vote], choiceIndexes[nonChoice]]++;
//}
}
// All unranked options are at distance 0 from each other, and thus have no effect
// on the distance table.
}
return(data);
}
