/// <summary>
/// Gets the top two rated options.
/// </summary>
/// <param name="rankedVotes">The group votes.</param>
/// <param name="option1">The top rated option. Null if there aren't any options available.</param>
/// <param name="option2">The second rated option. Null if there is only one option available.</param>
private static void GetTopTwoRatedOptions(IEnumerable<RankGroupedVoters> rankedVotes,
out string option1, out string option2, ref string debug)
{
var scoredVotes = from vote in rankedVotes
select new { Vote = vote.VoteContent, Rank = RankScoring.LowerWilsonScore(vote.Ranks) };
var orderedVotes = scoredVotes.OrderByDescending(a => a.Rank);
var topTwo = orderedVotes.Take(2);
var v1 = topTwo.FirstOrDefault();
var v2 = topTwo.Skip(1).FirstOrDefault();
option1 = v1?.Vote;
option2 = v2?.Vote;
StringBuilder sb = new StringBuilder();
// Output: [Option1, Option2] [Score1, Score2] [PrefCount1, PrefCount2]
sb.Append("RIR: [");
if (v1 != null)
sb.Append(v1.Vote);
sb.Append(", ");
if (v2 != null)
sb.Append(v2.Vote);
sb.Append("] [");
if (v1 != null)
sb.Append($"{v1.Rank:f5}");
sb.Append(", ");
if (v2 != null)
sb.Append($"{v2.Rank:f5}");
sb.Append("] ");
debug = sb.ToString();
}
/// <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)
{
// 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);
}
