public double Calculate(SimilarityList data)
{
var length = 0;
double sumX = 0;
double sumY = 0;
double sumX2 = 0;
double sumY2 = 0;
// ReSharper disable once InconsistentNaming
double sumXY = 0;
foreach (var value in data.Data)
{
sumX += value.Item1;
sumY += value.Item2;
sumX2 += Math.Pow(value.Item1, 2);
sumY2 += Math.Pow(value.Item2, 2);
sumXY += value.Item1 * value.Item2;
length++;
}
var numerator = sumXY - sumX * sumY / length;
var denominator = Math.Sqrt(sumX2 - Math.Pow(sumX, 2) / length) *
Math.Sqrt(sumY2 - Math.Pow(sumY, 2) / length);
return(numerator / denominator);
}
public double Calculate(SimilarityList data)
{
double multiSum = 0;
double sumX2 = 0;
double sumY2 = 0;
foreach (var value in data.ZerodData)
{
multiSum += value.Item1 * value.Item2;
sumX2 += Math.Pow(value.Item1, 2);
sumY2 += Math.Pow(value.Item2, 2);
}
return(multiSum / (Math.Sqrt(sumX2) * Math.Sqrt(sumY2)));
}
/// <summary>
/// Calculate similarity and return a list of tuples with the user and how similar it is.
/// </summary>
public IEnumerable <Tuple <User, float> > ListSimilarities(Similarity similarity, float threshold = 1)
{
var users = new List <Tuple <User, float> >();
foreach (var user in Users)
{
var data = new SimilarityList(user.Ratings, User.Ratings, Articles);
var result = (float)similarity.Calculate(data);
if (result < threshold)
{
continue;
}
users.Add(new Tuple <User, float>(user, result));
}
// Sort
users.Sort((x, y) => y.Item2.CompareTo(x.Item2));
return(users);
}
/// <summary>
/// Converts two lists together based on the articles.
/// </summary>
public SimilarityWrapper(SimilarityList data)
{
Data = data;
}
public double Distance(SimilarityList data)
{
return(Math.Sqrt((from value in data.Data select Math.Pow(value.Item1 - value.Item2, 2)).Sum()));
}
public double Calculate(SimilarityList data)
{
return(1 / (1 + Distance(data)));
}
public double Distance(SimilarityList data)
{
return((from value in data.Data select Math.Abs(value.Item1 - value.Item2)).Sum());
}