public static HCCluster Join(HCCluster a, HCCluster b)
{
List <HCPoint> pointList = new(a.Points);
pointList.AddRange(b.Points);
return(new(pointList));
}
public static List <HCCluster> ClusterPerPoint(List <HCPoint> points)
{
List <HCCluster> clusters = new();
foreach (HCPoint p in points)
{
clusters.Add(HCCluster.FromSinglePoint(p));
}
return(clusters);
}
public static double SingleLinkage(HCCluster a, HCCluster b)
{
double minDistance = double.PositiveInfinity;
for (var i = 0; i < a.Points.Count; i++)
{
for (var j = 0; j < b.Points.Count; j++)
{
minDistance = Math.Min(minDistance, Metric.Euclid(a.Points[i], b.Points[j]));
}
}
return(minDistance);
}
public bool Step()
{
var prevIteration = State.Iterations.Last();
if (prevIteration.Clusters.Count <= 1)
{
return(false);
}
if (MinClusters > 0 && prevIteration.Clusters.Count <= MinClusters)
{
return(false);
}
if (DistanceLimit > 0 && prevIteration.ClosestPair.Distance >= DistanceLimit)
{
return(false);
}
HCCluster clusterI = prevIteration.ClosestPair.I;
HCCluster clusterJ = prevIteration.ClosestPair.J;
HCCluster joinedCluster = HCCluster.Join(clusterI, clusterJ);
List <HCCluster> newClusters = new();
foreach (HCCluster oldCluster in prevIteration.Clusters)
{
if (oldCluster != clusterI && oldCluster != clusterJ)
{
newClusters.Add(oldCluster);
}
}
var closest = distanceMatrix.FindClosestPair(
clusterPairs: joinedCluster.PairsWith(newClusters),
metric: (joinedCluster, other) => distanceMatrix.LanceWillamsSingleLinkage(clusterI, clusterJ, other)
);
newClusters.Add(joinedCluster);
if (closest.Distance > prevIteration.ClosestPair.Distance)
{
closest = distanceMatrix.FindClosestPair(
clusterPairs: HCCluster.AllPairs(newClusters),
metric: distanceMatrix.GetDistance
);
}
State.Iterations.Add(new HCIteration(
clusters: newClusters,
closestPair: closest
));
return(true);
}
public void InitState(List <HCPoint> points)
{
State = new();
List <HCCluster> clusters = HCCluster.ClusterPerPoint(points);
HCClusterPair closest = distanceMatrix.FindClosestPair(
clusterPairs: HCCluster.AllPairs(clusters),
metric: Metric.SingleLinkage
);
State.Iterations.Add(new HCIteration(
clusters: clusters,
closestPair: closest
));
}
public HCClusterPair(HCCluster clusterI, HCCluster clusterJ, double distance)
{
I = clusterI;
J = clusterJ;
Distance = distance;
}
public static double LanceWillamsSingleLinkage(this IDistanceMatrix dm, HCCluster joinedA, HCCluster joinedB, HCCluster other)
{
return(0.5 * dm.GetDistance(joinedA, other)
+ 0.5 * dm.GetDistance(joinedB, other)
- 0.5 * Math.Abs(dm.GetDistance(joinedA, other) - dm.GetDistance(joinedB, other)));
}
