public List <MovieViewModel> GetSuggestions(string userId, int numSuggestions, UserMovieRatingsTable table)
{
int userIndex = table.UserIndexToId.IndexOf(userId);
UserMoviesRatings user = table.Users[userIndex];
List <Suggestion> suggestions = new List <Suggestion>();
List <UserMoviesRatings> neighbors = GetNearestNeighbors(userId, user, 5, table);
if (neighbors.ToList()[0].Score <= 0.5)
{
ItemBasedRecommender itemBasedRecommender = new ItemBasedRecommender(_mapper, _movieRepository);
return(itemBasedRecommender.GetSuggestions(userId, 10, table));
}
for (int movieIndex = 0; movieIndex < table.MovieIndexToId.Count; movieIndex++)
{
if (user.MovieRatings[movieIndex] != 0)
{
double score = 0.0;
int count = 0;
for (var u = 0; u < neighbors.Count; u++)
{
if (neighbors[u].MovieRatings[movieIndex] != 0)
{
score += neighbors[u].MovieRatings[movieIndex] - ((u + 1.0) / 100.0);
count++;
}
}
if (count > 0)
{
score /= count;
}
suggestions.Add(new Suggestion(userId, table.MovieIndexToId[movieIndex], score));
}
}
suggestions.Sort((c, n) => n.Rating.CompareTo(c.Rating));
List <Suggestion> suggestionsList = suggestions.Take(numSuggestions).ToList();
List <MovieViewModel> movieViewModels = new List <MovieViewModel>();
foreach (var suggestion in suggestionsList)
{
Movie movie = _movieRepository.GetById(suggestion.MovieId);
movieViewModels.Add(_mapper.Map <MovieViewModel>(movie));
}
return(movieViewModels);
}
private List <UserMoviesRatings> GetNearestNeighbors(string userId, UserMoviesRatings user, int numUsers, UserMovieRatingsTable table)
{
List <UserMoviesRatings> neighbors = new List <UserMoviesRatings>();
Methods pearsoneCorrelation = new Methods {
};
for (var i = 0; i < table.Users.Count(); i++)
{
if (table.Users[i].UserId == user.UserId)
{
table.Users[i].Score = double.NegativeInfinity;
}
else
{
table.Users[i].Score = pearsoneCorrelation.PearsoneCorrelation(table.Users[i].MovieRatings, user.MovieRatings);
}
}
var similarUsers = table.Users.OrderByDescending(x => x.Score);
return(similarUsers.Take(numUsers).ToList());
}
