// Note:
// -u can be up to N+i-1
// -l can be down to -N+1+u
private void CalculateNeighbourhood(IList<ScanPoint> scan, float eps, FloatMetric<ScanPoint> circularMetric)
{ //both the scan and feature space are circular which makes implemantation tricky!
int N=scan.Count, l = N-1, u = 0;
for (int i = 0; i < N; ++i)
{
for (; u < N + i && circularMetric.Distance(scan[Mod(u, N)], scan[i]) < eps; ++u)
;
U[i] = u-1;
}
for (int i = N-1; i >= 0; --i)
{
for(; U[i]-l+1<=N && circularMetric.Distance(scan[Mod(l, N)], scan[i]) < eps; --l)
;
L[i] = l+1;
}
}
public List<DBSCANCluster> Cluster(IList<ScanPoint> scan, float eps, int minPoints, Comparer<ScanPoint> comparer, FloatMetric<ScanPoint> circularMetric)
{
List<DBSCANCluster> clusters = new List<DBSCANCluster>();
int cluster = 0, N=scan.Count;
if (N > Capacity)
Capacity = N;
ArrayList.Adapter((IList)scan).Sort(comparer);
CalculateNeighbourhood(scan, eps, circularMetric);
for (int i = 0; i < N; ++i)
C[i] = NOT_VISITED;
for (int i = 0; i < N; ++i)
{
if (C[i] != NOT_VISITED)
continue;
if (NeighbourCount(i) < minPoints)
C[i] = NOISE;
else
clusters.Add(ExpandCluster(scan, ++cluster, i, minPoints));
}
// DumpScan(scan, C);
return clusters;
}