/// <summary>
/// Implementation to generate the ranking list for the provided set
/// of votes for a specific task.
/// </summary>
/// <param name="task">The task that the votes are grouped under.</param>
/// <returns>Returns a ranking list of winning votes.</returns>
protected override RankResults RankTask(GroupedVotesByTask task)
{
RankResults winningChoices = new RankResults();
// The groupVotes are used for getting the Wilson score
var rankedVotes = GroupRankVotes.GroupByVoteAndRank(task);
// The voterRankings are used for the runoff
var voterRankings = GroupRankVotes.GroupByVoterAndRank(task);
// The full choices list is just to keep track of how many we have left.
var allChoices = GroupRankVotes.GetAllChoices(voterRankings);
for (int i = 1; i <= 9; i++)
{
RankResult winner = GetWinningVote(voterRankings, rankedVotes);
if (winner == null)
{
break;
}
winningChoices.Add(winner);
allChoices.Remove(winner.Option);
if (!allChoices.Any())
{
break;
}
voterRankings = RemoveChoiceFromVotes(voterRankings, winner.Option);
rankedVotes = RemoveChoiceFromRanks(rankedVotes, winner.Option);
}
return(winningChoices);
}
/// <summary>
/// Gets the least preferred choice.
/// This is normally determined by selecting the option with the lowest Borda count.
/// This is inverted because we don't want to convert ranks to Borda values (it gains us nothing).
/// It then needs to be averaged across the number of instances of each vote, to
/// account for unranked options. This allows apples-to-apples comparisons against options
/// that are ranked in all votes.
/// We then need to scale it relative to the number of instances of that option appearing, to deal
/// with truncated rankings (where there are more options than rankings allowed).
/// An option ranked infrequently can be scaled up relative to its rate of occurance for
/// a high likelihood of elimination.
/// </summary>
/// <param name="localRankings">The vote rankings.</param>
/// <returns>Returns the vote string for the least preferred vote.</returns>
private static string GetLeastPreferredChoice(List <VoterRankings> localRankings)
{
var groupVotes = GroupRankVotes.GroupByVoteAndRank(localRankings);
var rankedVotes = from vote in groupVotes
select new { Vote = vote.VoteContent, Rank = RankScoring.LowerWilsonScore(vote.Ranks) };
var worstVote = rankedVotes.MinObject(a => a.Rank);
Debug.Write($"({worstVote.Rank:f5}) {worstVote.Vote}");
return(worstVote.Vote);
}
/// <summary>
/// Implementation to generate the ranking list for the provided set
/// of votes for a specific task.
/// </summary>
/// <param name="task">The task that the votes are grouped under.</param>
/// <returns>Returns a ranking list of winning votes.</returns>
protected override RankResults RankTask(GroupedVotesByTask task)
{
var groupVotes = GroupRankVotes.GroupByVoteAndRank(task);
var rankedVotes = from vote in groupVotes
select new { Vote = vote.VoteContent, Rank = RankVote(vote.Ranks) };
var orderedVotes = rankedVotes.OrderByDescending(a => a.Rank);
RankResults results = new RankResults();
results.AddRange(orderedVotes.Select(a =>
new RankResult(a.Vote, $"BordaRank: [{a.Rank}]")));
return(results);
}
/// <summary>
/// Implementation to generate the ranking list for the provided set
/// of votes for a specific task.
/// </summary>
/// <param name="task">The task that the votes are grouped under.</param>
/// <returns>Returns a ranking list of winning votes.</returns>
protected override RankResults RankTask(GroupedVotesByTask task)
{
// Can calculating the score easily by having all the rankings for
// each vote grouped together.
var groupVotes = GroupRankVotes.GroupByVoteAndRank(task);
var rankedVotes = from vote in groupVotes
select new { Vote = vote.VoteContent, Rank = RankScoring.LowerWilsonScore(vote.Ranks) };
var orderedVotes = rankedVotes.OrderByDescending(a => a.Rank);
RankResults results = new RankResults();
results.AddRange(orderedVotes.Select(a =>
new RankResult(a.Vote, $"Wilson: [{a.Rank:f5}]")));
return(results);
}
/// <summary>
/// Implementation to generate the ranking list for the provided set
/// of votes for a specific task.
/// </summary>
/// <param name="task">The task that the votes are grouped under.</param>
/// <returns>Returns a ranking list of winning votes.</returns>
protected override RankResults RankTask(GroupedVotesByTask task)
{
Debug.WriteLine(">>Normalized Borda Counting<<");
//var voterCount = task.SelectMany(t => t.Value).Distinct().Count();
var groupVotes = GroupRankVotes.GroupByVoteAndRank(task);
var rankedVotes = from vote in groupVotes
select new { Vote = vote.VoteContent, Rank = RankVote(vote.Ranks) };
var orderedVotes = rankedVotes.OrderBy(a => a.Rank);
RankResults results = new RankResults();
results.AddRange(orderedVotes.Select(a =>
new RankResult(a.Vote, $"BordaNorm: [{a.Rank:f5}]")));
return(results);
}
