public NearestNeighbours(Dictionary <int, Dictionary <int, double> > ratings, int userId, ISimilarity similarityFunction, int maxNeighbours, double threshold)
{
// loop over the users in the dictionary
foreach (var user in ratings)
{
// only consider the ratings of the users that are not our target user
if (user.Key != userId)
{
Tuple <Vector, Vector> commonRatings;
if (similarityFunction.GetType() != typeof(Cosine))
{
commonRatings = CommonRatings.getCommonRatings(ratings[userId], user.Value);
}
else
{
commonRatings = CommonRatings.getCosineRatings(ratings[userId], user.Value);
}
var newSimilarity = similarityFunction.getSimilarity(commonRatings.Item1, commonRatings.Item2);
var anotherRating = anotherRatingYesOrNo(ratings[userId], user.Value);
if (newSimilarity > threshold && anotherRating)
{
if (nearestNeighbours.Count() < maxNeighbours)
{
nearestNeighbours.Add(user.Key, newSimilarity);
}
else
{
var oldSimilarity = nearestNeighbours.OrderBy(y => y.Value).First();
if (newSimilarity > oldSimilarity.Value)
{
nearestNeighbours.Remove(oldSimilarity.Key);
nearestNeighbours.Add(user.Key, newSimilarity);
}
}
}
if (nearestNeighbours.Count() == maxNeighbours)
{
threshold = nearestNeighbours.Values.Min();
}
}
}
}
static void Main(string[] args)
{
Console.WriteLine("|| Assignment 1: User-Item ||");
Console.WriteLine();
var ratings = Parser.Parse(',', "./userItem.data");
var commonRatings3and4 = CommonRatings.getCommonRatings(ratings[3], ratings[4]);
var pearson = new Pearson();
var pearson3and4 = pearson.getSimilarity(commonRatings3and4.Item1, commonRatings3and4.Item2);
Console.WriteLine("// Pearson coefficient of similarity between users 3 and 4: " + pearson3and4);
Console.WriteLine();
Console.WriteLine("// Nearest neighbours and similarities for user 7 (using pearson): ");
var nearestNeighbourUser7Pearson = new NearestNeighbours(ratings, 7, new Pearson(), 3, 0.35);
foreach (var nearestNeighbor in nearestNeighbourUser7Pearson.nearestNeighbours.OrderByDescending(x => x.Value))
{
Console.WriteLine("User " + nearestNeighbor.Key + " = Similarity: " + nearestNeighbor.Value);
}
Console.WriteLine("// Nearest neighbours and similarities for user 7 (using cosine): ");
var nearestNeighbourUser7Cosine = new NearestNeighbours(ratings, 7, new Cosine(), 3, 0.35);
foreach (var nearestNeighbor in nearestNeighbourUser7Cosine.nearestNeighbours.OrderByDescending(x => x.Value))
{
Console.WriteLine("User " + nearestNeighbor.Key + " = Similarity: " + nearestNeighbor.Value);
}
Console.WriteLine("// Nearest neighbours and similarities for user 7 (using euclidean): ");
var nearestNeighbourUser7Euclidean = new NearestNeighbours(ratings, 7, new Euclidean(), 3, 0.35);
foreach (var nearestNeighbor in nearestNeighbourUser7Euclidean.nearestNeighbours.OrderByDescending(x => x.Value))
{
Console.WriteLine("User " + nearestNeighbor.Key + " = Similarity: " + nearestNeighbor.Value);
}
Console.WriteLine();
Console.WriteLine("// Predicted ratings for user 7 (using pearson): ");
var predictedRatingUser7item101 = Prediction.getPrediction(ratings, nearestNeighbourUser7Pearson.nearestNeighbours, 7, 101);
Console.WriteLine("Item 101 has a predicted rating of: " + predictedRatingUser7item101);
var predictedRatingUser7item103 = Prediction.getPrediction(ratings, nearestNeighbourUser7Pearson.nearestNeighbours, 7, 103);
Console.WriteLine("Item 103 has a predicted rating of: " + predictedRatingUser7item103);
var predictedRatingUser7item106 = Prediction.getPrediction(ratings, nearestNeighbourUser7Pearson.nearestNeighbours, 7, 106);
Console.WriteLine("Item 106 has a predicted rating of: " + predictedRatingUser7item106);
Console.WriteLine();
Console.WriteLine("// Predicted Rating for user 4 (using pearson): ");
var nearestNeighbourUser4Pearson = new NearestNeighbours(ratings, 4, new Pearson(), 3, 0.35);
var predictedRatingUser4item101 = Prediction.getPrediction(ratings, nearestNeighbourUser4Pearson.nearestNeighbours, 4, 101);
Console.WriteLine("Item 101 has a predicted rating of: " + predictedRatingUser4item101);
Console.WriteLine();
Console.WriteLine("// Adjusted 106 Rating to 2.8 for user 7 (using pearson) gives predictions: ");
ratings[7][106] = 2.8;
var nearestNeighbourUser7PearsonAdj1 = new NearestNeighbours(ratings, 7, new Pearson(), 3, 0.35);
var predictedRatingUser7Adjusted1item101 = Prediction.getPrediction(ratings, nearestNeighbourUser7PearsonAdj1.nearestNeighbours, 7, 101);
var predictedRatingUser7Adjusted1item103 = Prediction.getPrediction(ratings, nearestNeighbourUser7PearsonAdj1.nearestNeighbours, 7, 103);
Console.WriteLine("Item 101 has a predicted rating of: " + predictedRatingUser7Adjusted1item101);
Console.WriteLine("Item 103 has a predicted rating of: " + predictedRatingUser7Adjusted1item103);
Console.WriteLine();
Console.WriteLine("// Adjusted 106 Rating to 5 for user 7 (using pearson) gives predictions: ");
ratings[7][106] = 5;
var nearestNeighbourUser7PearsonAdj2 = new NearestNeighbours(ratings, 7, new Pearson(), 3, 0.35);
var predictedRatingUser7Adjusted2item101 = Prediction.getPrediction(ratings, nearestNeighbourUser7PearsonAdj2.nearestNeighbours, 7, 101);
var predictedRatingUser7Adjusted2item103 = Prediction.getPrediction(ratings, nearestNeighbourUser7PearsonAdj2.nearestNeighbours, 7, 103);
Console.WriteLine("Item 101 has a predicted rating of: " + predictedRatingUser7Adjusted2item101);
Console.WriteLine("Item 103 has a predicted rating of: " + predictedRatingUser7Adjusted2item103);
Console.WriteLine();
var movieRatings = Parser.Parse('\t', "u.data");
Console.WriteLine("// After importing the movie dataset, the top 8 recommendations for user 186: ");
var movieUser186Pearson = new NearestNeighbours(movieRatings, 186, new Pearson(), 25, 0.35);
var movieUser186PearsonTop8 = Prediction.getTopPredictions(movieRatings, movieUser186Pearson.nearestNeighbours, 186, 0, 8);
foreach (var prediction in movieUser186PearsonTop8)
{
Console.WriteLine("Movie: {0} has a rating of {1}", prediction.Key, prediction.Value);
}
Console.WriteLine();
Console.WriteLine("// The top 8 recommendations for user 186 with at least three nearest neighbours: ");
var movieUser186PearsonTop8Adj = Prediction.getTopPredictions(movieRatings, movieUser186Pearson.nearestNeighbours, 186, 3, 8);
foreach (var prediction in movieUser186PearsonTop8Adj)
{
Console.WriteLine("Movie: {0} has a rating of {1}", prediction.Key, prediction.Value);
}
Console.WriteLine();
//Console.WriteLine("Parsed Data file: ");
//foreach (var outerEntry in ratings)
//{
// foreach (var innerEntry in outerEntry.Value)
// {
// Console.WriteLine("User:{0} Key:{1} Value:{2}", outerEntry.Key, innerEntry.Key, innerEntry.Value);
// }
//}
Console.ReadLine();
}
