static List <PointInfo> GetRegion(List <PointInfo> points, PointInfo p, double eps)
{
List <PointInfo> region = new List <PointInfo>();
for (int i = 0; i < points.Count; i++)
{
int distSquared = PointInfo.DistanceSquared(p, points[i]);
if (distSquared <= eps)
{
region.Add(points[i]);
}
}
return(region);
}
//**********************************DBSCAN Alghorithm *******************************************************
static public List <List <PointInfo> > GetClusters(List <PointInfo> points, double eps, int minPts)
{
if (points == null)
{
return(null);
}
List <List <PointInfo> > clusters = new List <List <PointInfo> >();
eps *= eps; // square eps
int clusterId = 1;
for (int i = 0; i < points.Count; i++)
{
PointInfo p = points[i];
if (p.ClusterId == PointInfo.UNCLASSIFIED)
{
if (ExpandCluster(points, p, clusterId, eps, minPts))
{
clusterId++;
}
}
}
// sort out points into their clusters, if any
int maxClusterId = points.OrderBy(p => p.ClusterId).Last().ClusterId;
if (maxClusterId < 1)
{
return(clusters); // no clusters, so list is empty
}
for (int i = 0; i < maxClusterId; i++)
{
clusters.Add(new List <PointInfo>());
}
foreach (PointInfo p in points)
{
if (p.ClusterId > 0)
{
clusters[p.ClusterId - 1].Add(p);
}
}
return(clusters);
}
static bool ExpandCluster(List <PointInfo> points, PointInfo p, int clusterId, double eps, int minPts)
{
List <PointInfo> seeds = GetRegion(points, p, eps);
if (seeds.Count < minPts) // no core point
{
p.ClusterId = PointInfo.NOISE;
return(false);
}
else // all points in seeds are density reachable from point 'p'
{
for (int i = 0; i < seeds.Count; i++)
{
seeds[i].ClusterId = clusterId;
}
seeds.Remove(p);
while (seeds.Count > 0)
{
PointInfo currentP = seeds[0];
List <PointInfo> result = GetRegion(points, currentP, eps);
if (result.Count >= minPts)
{
for (int i = 0; i < result.Count; i++)
{
PointInfo resultP = result[i];
if (resultP.ClusterId == PointInfo.UNCLASSIFIED || resultP.ClusterId == PointInfo.NOISE)
{
if (resultP.ClusterId == PointInfo.UNCLASSIFIED)
{
seeds.Add(resultP);
}
resultP.ClusterId = clusterId;
}
}
}
seeds.Remove(currentP);
}
return(true);
}
}