private Similarity GetSimilarityToRater(RaterBase rater1, RaterBase rater2)
{
// do some linq magic to get our variables for the forumula -- this builds the similarity value between rater1 and rater2
//S(U1, U2) = ((L1 intersection L2) + (D1 intersection d2) - (L1 intersection D2) - (L2 intersection D1)) / (L1 union L2 union D1 union D2)
// (L1 intersection L2)
var listRater1LikeRater2LikeIntersection = rater1.Likes.Intersect(rater2.Likes);
// (D1 intersection d2)
var listRater1DisLikeRater2DisLikeIntersection = rater1.Dislikes.Intersect(rater2.Dislikes);
// (L1 intersection D2)
var listRater1LikeRater2DisLikeIntersection = rater1.Likes.Intersect(rater2.Dislikes);
// (L2 intersection D1)
var listRater1DisLikeRater2LikeIntersection = rater2.Likes.Intersect(rater1.Dislikes);
var divisor = rater1.Likes.Union(rater2.Likes).Union(rater1.Dislikes).Union(rater2.Dislikes);
double similarity = RunSimilarityFormula(listRater1LikeRater2LikeIntersection.Count(), listRater1DisLikeRater2DisLikeIntersection.Count(),
listRater1LikeRater2DisLikeIntersection.Count(), listRater1DisLikeRater2LikeIntersection.Count(),
divisor.Count());
if (similarity == double.NaN)
{
similarity = 0.0;
}
return(new Similarity()
{
Rater = rater2, Value = similarity
});
}
public void AddUserActionsToLikes(string userAction)
{
List <UserAction> listUserActions = Ratings.Where(s => s.Action.Equals(userAction)).ToList();
this.Likes.AddRange(listUserActions);
foreach (UserAction uA in listUserActions)
{
RaterBase rater = Raters.FirstOrDefault(s => s.Id == uA.Rater.Id);
if (rater != null)
{
rater.Likes.Add(uA.Ratee);
}
}
}
private double GetProbabilityUserLikesRatee(RaterBase user, RateeBase ratee)
{
// P(U,A) = (Zl - Zd) / (Ml + Md)
// Zl computations
// sum of user's similarities to our user who have liked the ratee in question
var similaritesForRatersWhoLikedRatee = user.Similarities.Where(s => ratee.Likes.Contains(s.Rater));
double Zl = 0.0;
foreach (Similarity similar in similaritesForRatersWhoLikedRatee)
{
Zl += similar.Value;
}
// Ml computations
// total who have liked ratee
int Ml = ratee.Likes.Count();
// Zd computations
// sum of user's similarities to our user who have disliked the ratee in question
var similaritesForRatersWhoDislikedRatee = user.Similarities.Where(s => ratee.Dislikes.Contains(s.Rater));
double Zd = 0.0;
foreach (Similarity similar in similaritesForRatersWhoDislikedRatee)
{
Zd += similar.Value;
}
// Md computations
// total who have disliked ratee
int Md = ratee.Dislikes.Count();
double probability = 0.0;
// if ( (Ml + Md) != 0.0 && (Zl - Zd) != 0)
probability = RunProbabilityFormula(Zl, Zd, Ml, Md);
if (probability == double.NaN)
{
probability = 0.0;
}
return(probability);
}
public void RemoveUserActionsFromLikes(string userAction)
{
List <UserAction> listUserActions = Ratings.Where(s => s.Action.Equals(userAction)).ToList();
for (int index = listUserActions.Count() - 1, count = 0; count < listUserActions.Count() - 1; index--, count++)
{
this.Likes.RemoveAt(index);
}
for (int index = listUserActions.Count() - 1; index >= 0; index--)
{
UserAction uA = listUserActions[index];
RaterBase rater = Raters.FirstOrDefault(s => s.Id == uA.Rater.Id);
if (rater != null)
{
rater.Likes.RemoveAt(rater.Likes.Count() - 1);
}
}
}
private List <Similarity> GetSimularities(RaterBase rater)
{
List <Similarity> simularities = new List <Similarity>();
foreach (RaterBase rater2 in Raters)
{
if (rater.Equals(rater2) == true)
{
continue;
}
Similarity sim = GetSimilarityToRater(rater, rater2);
if (sim.Value != 0.0)
{
simularities.Add(sim);
}
}
return(simularities);
}
