public static double Predicted(Dictionary <int, double> neighbours, Hashmap ratings, int item)
{
double c1 = 0;
double c2 = 0;
foreach (var kvpair in neighbours)
{
if (ratings.GetEntry(kvpair.Key).GetInnerDict().ContainsKey(item))
{
c1 += neighbours[kvpair.Key] * ratings.GetEntry(kvpair.Key).GetValueAtKey(item);
c2 += neighbours[kvpair.Key];
}
}
return(c1 / c2);
}
public static double Pearson(Hashmap ratings, int user_one, int user_two, Boolean nn)
{
double sx = 0, sy = 0, summ = 0, ssx = 0, ssy = 0;
var n = 0;
var user_one_ratings = ratings.GetEntry(user_one).GetInnerDict();
var user_two_ratings = ratings.GetEntry(user_two).GetInnerDict();
var similairRatingOne = new List <double>();
var similairRatingTwo = new List <double>();
foreach (var kvpair in user_one_ratings)
{
if (user_two_ratings.ContainsKey(kvpair.Key))
{
similairRatingOne.Add(user_one_ratings[kvpair.Key]);
similairRatingTwo.Add(user_two_ratings[kvpair.Key]);
}
}
if (similairRatingOne.Count == similairRatingTwo.Count)
{
n = similairRatingOne.Count;
}
if (n == 0 && nn == false)
{
throw new Exception("No items for users");
}
for (var i = 0; i < n; i++)
{
summ += similairRatingOne[i] * similairRatingTwo[i];
sx += similairRatingOne[i];
sy += similairRatingTwo[i];
ssx += Pow(similairRatingOne[i], 2);
ssy += Pow(similairRatingTwo[i], 2);
}
var c1 = summ - sx * sy / n;
var c2 = Sqrt(ssx - Pow(sx, 2) / n);
var c3 = Sqrt(ssy - Pow(sy, 2) / n);
return(c1 / (c2 * c3));
}
public static double Generalised(Hashmap ratings, int r, int user_one, int user_two, int item)
{
var user_one_ratings = ratings.GetEntry(user_one).GetInnerDict();
var user_two_ratings = ratings.GetEntry(user_two).GetInnerDict();
double sums = 0;
if (user_two_ratings.ContainsKey(item) && user_one_ratings.ContainsKey(item))
{
sums += Pow(Abs(user_one_ratings[item] - user_two_ratings[item]), r);
}
else
{
throw new Exception("No item for users");
}
var answer = Pow(sums, 1 / r);
return(Similarity(answer));
}
public static double Cosine(Hashmap ratings, int user_one, int user_two)
{
double summ = 0, ssx = 0, ssy = 0;
var n = 0;
var user_one_ratings = ratings.GetEntry(user_one).GetInnerDict();
var user_two_ratings = ratings.GetEntry(user_two).GetInnerDict();
var similairRatingOne = new List <double>();
var similairRatingTwo = new List <double>();
foreach (var kvpair in user_one_ratings)
{
if (user_two_ratings.ContainsKey(kvpair.Key) && user_one_ratings.ContainsKey(kvpair.Key))
{
similairRatingOne.Add(user_one_ratings[kvpair.Key]);
similairRatingTwo.Add(user_two_ratings[kvpair.Key]);
}
else
{
throw new Exception("No sim");
}
}
if (similairRatingOne.Count == similairRatingTwo.Count)
{
n = similairRatingOne.Count;
}
for (var i = 0; i < n; i++)
{
summ += similairRatingOne[i] * similairRatingTwo[i];
ssx += Pow(similairRatingOne[i], 2);
ssy += Pow(similairRatingTwo[i], 2);
}
return(summ / (Sqrt(ssx) * Sqrt(ssy)));
}
