/// <summary>
/// Starts the clustering.
/// </summary>
/// <param name="elements"></param>
/// <param name="fusion"></param>
/// <param name="metric"></param>
/// <returns></returns>
protected internal Cluster[] Cluster(List<Element> elements, Fusion fusion, IDistanceMetric metric)
{
HashSet<Cluster> clusters = new HashSet<Cluster>();
ClusterPairs pairs = new ClusterPairs();
// 1. Initialize each element as a cluster
foreach (Element el in elements)
{
Cluster cl = new Cluster(fusion);
cl.AddElement(el);
clusters.Add(cl);
}
// 2. a) Calculate the distances of all clusters to all other clusters
foreach (Cluster cl1 in clusters)
{
foreach (Cluster cl2 in clusters)
{
if (cl1 == cl2)
continue;
ClusterPair pair = new ClusterPair(cl1, cl2, cl1.CalculateDistance(cl2));
pairs.AddPair(pair);
}
}
// 2. b) Initialize the pair with the lowest distance to each other.
ClusterPair lowestDistancePair = pairs.LowestDistancePair;
// 3. Merge clusters to new clusters and recalculate distances in a loop until there are only countCluster clusters
while (!isFinished(clusters, lowestDistancePair))
{
// a) Merge: Create a new cluster and add the elements of the two old clusters
lowestDistancePair = pairs.LowestDistancePair;
Cluster newCluster = new Cluster(fusion);
newCluster.AddElements(lowestDistancePair.Cluster1.GetElements());
newCluster.AddElements(lowestDistancePair.Cluster2.GetElements());
// b)Remove the two old clusters from clusters
clusters.Remove(lowestDistancePair.Cluster1);
clusters.Remove(lowestDistancePair.Cluster2);
// c) Remove the two old clusters from pairs
pairs.RemovePairsByOldClusters(lowestDistancePair.Cluster1, lowestDistancePair.Cluster2);
// d) Calculate the distance of the new cluster to all other clusters and save each as pair
foreach (Cluster cluster in clusters)
{
ClusterPair pair = new ClusterPair(cluster, newCluster, cluster.CalculateDistance(newCluster));
pairs.AddPair(pair);
}
// e) Add the new cluster to clusters
clusters.Add(newCluster);
}
return clusters.ToArray<Cluster>();
}
internal void RemovePairsByOldClusters(Cluster cluster1, Cluster cluster2)
{
List<ClusterPair> toRemove = new List<ClusterPair>();
foreach(ClusterPair pair in pairs)
{
if (pair.HasCluster(cluster1) || pair.HasCluster(cluster2))
{
toRemove.Add(pair);
}
}
foreach (ClusterPair pair in toRemove)
{
pairs.Remove(pair);
}
}
internal bool HasCluster(Cluster cluster)
{
return cluster1 == cluster || cluster2 == cluster;
}
internal float CalculateDistance(Cluster otherCluster)
{
return fusion.CalculateDistance(this, otherCluster);
}
public ClusterPair(Cluster cluster1, Cluster cluster2, float distance)
{
this.cluster1 = cluster1;
this.cluster2 = cluster2;
this.distance = distance;
}