public IEnumerable <KeyValuePair <int, double> > GetTopNItems(int userId, int n)
{
IPrediction userPrediction = new WeightedPrediction();
Dictionary <int, double> allItemPrediction = userPrediction.GetAllItemsPrediction(userId);
var topNItems = allItemPrediction
.OrderByDescending(s => s.Value)
.Take(n);
return(topNItems);
}
public static double Evaluate(int userId)
{
List <int> ratedItems = UserService.GetRatedItems(userId);
IPrediction prediction = new WeightedPrediction();
int N = ratedItems.Count;
double absoluteError = 0d;
foreach (var ratedItem in ratedItems)
{
double predicateRate = prediction.Predict(userId, ratedItem);
double realRate = RatingService.GetRate(userId, ratedItem);
absoluteError += Math.Abs(predicateRate - realRate);
}
return(absoluteError / (double)N);
}
public static double Evaluate()
{
List <int> userIds = DataStore.AllRatings
.Select(s => s.UserId)
.Distinct()
.ToList();
int N = DataStore.AllRatings.Count;
double absoluteError = 0d;
foreach (var userId in userIds)
{
List <int> ratedItems = UserService.GetRatedItems(userId);
IPrediction prediction = new WeightedPrediction();
foreach (var ratedItem in ratedItems)
{
double predicateRate = prediction.Predict(userId, ratedItem);
double realRate = RatingService.GetRate(userId, ratedItem);
absoluteError += Math.Abs(predicateRate - realRate);
}
}
return(absoluteError / (double)N);
}
