/// <summary>
/// Finds the K nearest instances to the test instance.
/// </summary>
/// <param name="test">The test instance.</param>
/// <returns>An array of the k-nearest results.</returns>
/// <remarks></remarks>
public Result[] FindKNearest(Instance test)
{
List<Result> results = new List<Result>();
foreach (Instance train in TrainingInstances)
{
double dist = double.MaxValue;
switch (Metric)
{
case Metric.DistanceSquared: dist = train.DistanceSquared(test); break;
case Metric.EuclideanDistance: dist = train.EuclideanDistance(test); break;
case Metric.ManhattanDistance: dist = train.ManhattanDistance(test); break;
case Metric.ChebyshevDistance: dist = train.ChebyshevDistance(test); break;
case Metric.CosineSimilarity: dist = 1 - train.CosineSimilarity(test); break;
case Metric.PearsonSimilarity: dist = 1 - train.PearsonSimilarity(test); break;
case Metric.JaccardSimilarity: dist = 1 - train.JaccardSimilarity(test); break;
default: throw new NotSupportedException();
}
results.Add(new Result(train.Class, dist));
}
int k = (int)Math.Min(K, TrainingInstances.Count);
results.Sort();
Result[] knr = new Result[k];
results.CopyTo(0, knr, 0, k);
return knr;
}
/// <summary> /// Classifies the specified test instance. /// </summary> /// <param name="test">The test instance.</param> /// <returns>A classification result.</returns> /// <remarks></remarks> public abstract Result Classify(Instance test);
/// <summary>
/// Calculates the Jaccard similarity of this instance with a specified instance.
/// </summary>
/// <param name="vector">The instance.</param>
/// <returns>The Jaccard similarity.</returns>
/// <remarks></remarks>
public double JaccardSimilarity(Instance vector)
{
double m11 = 0;
for (int i = 0; i < Features.Length; i += 1)
{
m11 += (Features[i] == vector.Features[i]) ? 1 : 0;
}
return m11 / Features.Length;
}
/// <summary>
/// Classifies the specified test instance.
/// </summary>
/// <param name="test">The test instance.</param>
/// <returns></returns>
/// <remarks></remarks>
public override Result Classify(Instance test)
{
return FindMaxClass(FindKNearest(test));
}
/// <summary>
/// Calculates the Cosine similarity of this instance with a specified instance.
/// </summary>
/// <param name="vector">The instance.</param>
/// <returns>The Cosine similarity.</returns>
/// <remarks></remarks>
public double CosineSimilarity(Instance vector)
{
return DotProduct(vector) / (Length() * vector.Length());
}
/// <summary>
/// Calculates the Pearson similarity of this instance with a specified instance.
/// </summary>
/// <param name="vector">The instance.</param>
/// <returns>The Pearson similarity.</returns>
/// <remarks></remarks>
public double PearsonSimilarity(Instance vector)
{
double meanx = Mean(), meany = vector.Mean();
double sdx = StandardDeviation(), sdy = vector.StandardDeviation();
double sum = 0;
for (int i = 0; i < Features.Length; i += 1)
{
sum += ((Features[i] - meanx) / sdx) * ((vector.Features[i] - meany) / sdy);
}
return sum / Features.Length;
}
/// <summary>
/// Calculates the Chebyshev distance of this instance to a specified instance.
/// </summary>
/// <param name="vector">The instance.</param>
/// <returns>The chebyshev distance.</returns>
/// <remarks></remarks>
public double ChebyshevDistance(Instance vector)
{
double max = double.NegativeInfinity, dist = 0;
for (int i = 0; i < Features.Length; i += 1)
{
dist = Math.Abs(vector.Features[i] - Features[i]);
if (dist > max) max = dist;
}
return dist;
}
/// <summary>
/// Calculates the Minkowski distance of this instance to a specified instance.
/// </summary>
/// <param name="vector">The instance.</param>
/// <param name="power">The Minkowski power.</param>
/// <returns></returns>
/// <remarks></remarks>
public double MinkowskiDistance(Instance vector, double power)
{
double sum = 0;
for (int i = 0; i < Features.Length; i += 1)
{
sum += Math.Pow(Math.Abs(vector.Features[i] - Features[i]), power);
}
return Math.Pow(sum, 1 / power);
}
/// <summary>
/// Calculates the Manhattan distance of this instance to a specified instance.
/// </summary>
/// <param name="vector">The instance.</param>
/// <returns>The Manhattan distance.</returns>
/// <remarks></remarks>
public double ManhattanDistance(Instance vector)
{
double sum = 0;
for (int i = 0; i < Features.Length; i += 1)
{
sum += Math.Abs(vector.Features[i] - Features[i]);
}
return sum;
}
/// <summary>
/// Calculates the Euclidean distance of this instance to a specified instance.
/// </summary>
/// <param name="vector">The instance.</param>
/// <returns>The distance.</returns>
/// <remarks></remarks>
public double EuclideanDistance(Instance vector)
{
return Math.Sqrt(DistanceSquared(vector));
}
/// <summary>
/// Calculates the squared Euclidean distance of this instance to a specified instance.
/// </summary>
/// <param name="vector">The instance.</param>
/// <returns>The squared distance.</returns>
/// <remarks></remarks>
public double DistanceSquared(Instance vector)
{
double sum = 0;
for (int i = 0; i < Features.Length; i += 1)
{
sum += (vector.Features[i] - Features[i])
* (vector.Features[i] - Features[i]);
}
return sum;
}
/// <summary>
/// Performs the vector dot-product of this instance's features and a specified instance's.
/// </summary>
/// <param name="vector">The instance to dot with.</param>
/// <returns>The dot product.</returns>
/// <remarks></remarks>
public double DotProduct(Instance vector)
{
double sum = 0;
for (int i = 0; i < Features.Length; i += 1)
{
sum += vector.Features[i] * Features[i];
}
return sum;
}
/// <summary>
/// Classifies the specified test instance.
/// </summary>
/// <param name="test">The test instance.</param>
/// <returns></returns>
/// <remarks></remarks>
public override Result Classify(Instance test)
{
string maxClass = "?";
double maxProb = float.MinValue;
double[] features = FeatureReduction.Discretize(test.Features, 10);
foreach (KeyValuePair<string, double> pair in Classes)
{
double score = Math.Log(pair.Value / TotalExamples);
for (int i = 0; i < features.Length; i++)
{
score += Math.Log(Count(pair.Key, i, features[i]) / pair.Value);
}
if (score > maxProb)
{
maxProb = score;
maxClass = pair.Key;
}
}
return new Result(maxClass, maxProb);
}
