private static Cluster<T> BuildCluster<T>(ISpatialIndex<PointInfo<T>> index, PointInfo<T> point, IReadOnlyList<PointInfo<T>> neighborhood, double epsilon, int minimumPointsPerCluster)
where T : IPointData
{
var points = new List<T>() { point.Item };
var cluster = new Cluster<T>() { Objects = points };
point.Cluster = cluster;
var queue = new Queue<PointInfo<T>>(neighborhood);
while (queue.Any())
{
var newPoint = queue.Dequeue();
if (!newPoint.Visited)
{
newPoint.Visited = true;
var newNeighbors = index.Search(newPoint.Point, epsilon);
if (newNeighbors.Count >= minimumPointsPerCluster)
foreach (var p in newNeighbors)
queue.Enqueue(p);
}
if (newPoint.Cluster == null)
{
newPoint.Cluster = cluster;
points.Add(newPoint.Item);
}
}
return cluster;
}
public IEnumerable <IVectorFeature> GetFeatureByRange(Envelope env)
{
var featureIds = _SpatialIndex.Search(env);
foreach (var fid in featureIds)
{
yield return(GetFeatureByID(fid));
}
}
public static ClusterSet<T> CalculateClusters<T>(
ISpatialIndex<PointInfo<T>> index,
double epsilon,
int minimumPointsPerCluster)
where T : IPointData
{
var points = index.Search().ToList();
var clusters = new List<Cluster<T>>();
foreach (var p in points)
{
if (p.Visited) continue;
p.Visited = true;
var candidates = index.Search(p.Point, epsilon);
if (candidates.Count >= minimumPointsPerCluster)
{
clusters.Add(
BuildCluster(
index,
p,
candidates,
epsilon,
minimumPointsPerCluster));
}
}
return new ClusterSet<T>
{
Clusters = clusters,
UnclusteredObjects = points
.Where(p => p.Cluster == null)
.Select(p => p.Item)
.ToList(),
};
}
/// <inheritdoc />
public IObservable <Element> Get(BoundingBox bbox, int zoomLevel)
{
return(SpatialIndexTree.Search(bbox)
.ObserveOn(Scheduler.CurrentThread)
.Select((offset) => ElementStore.Get(offset)));
}