/// <summary>
/// Get k nearest neighbors of an instance.
/// </summary>
/// <param name="testingInstance">The instance to be used as a reference based on which distances to all other instances are calculated. </param>
/// <param name="k">Number of neighbors to be selected. </param>
/// <returns>Instances that are nearest to the testingInstance by Euclidean distance. </returns>
private IEnumerable <Instance> GetNeighbors(Instance testingInstance, int k)
{
Dictionary <Instance, double> distStats = new Dictionary <Instance, double>();
TrainingInstances.ForEach(i => distStats.Add(i, EuclideanDistance(testingInstance, i)));
distStats.Remove(testingInstance);
distStats = distStats.OrderBy(kvp => kvp.Value).Take(k).ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
foreach (KeyValuePair <Instance, double> kvp in distStats)
{
yield return(kvp.Key);
}
}
