/***************************************************/
/**** Public Methods ****/
/***************************************************/
public static List <List <T> > ClusterDBSCAN <T>(this List <T> items, Func <T, T, bool> metricFunction, int minCount = 1)
{
DBSCANObject <T>[] DBSCANItems = items.Select(x => Create.DBSCANObject <T>(x)).ToArray();
int c = 0;
for (int i = 0; i < DBSCANItems.Length; i++)
{
DBSCANObject <T> p = DBSCANItems[i];
if (p.IsVisited)
{
continue;
}
p.IsVisited = true;
DBSCANObject <T>[] neighbourItems = null;
RegionQuery(DBSCANItems, p.ClusterItem, metricFunction, out neighbourItems);
if (neighbourItems.Length < minCount)
{
p.ClusterId = -1;
}
else
{
c++;
ExpandCluster(DBSCANItems, p, neighbourItems, metricFunction, c, minCount);
}
}
List <List <T> > clusters = new List <List <T> >(
DBSCANItems
.Where(x => x.ClusterId > 0)
.GroupBy(x => x.ClusterId)
.Select(x => x.Select(y => y.ClusterItem).ToList())
);
return(clusters);
}
/***************************************************/
/**** Private methods ****/
/***************************************************/
private static void ExpandCluster <T>(DBSCANObject <T>[] allItems, DBSCANObject <T> item, DBSCANObject <T>[] neighbourItems, Func <T, T, bool> metricFunction, int c, int minCount)
{
item.ClusterId = c;
for (int i = 0; i < neighbourItems.Length; i++)
{
DBSCANObject <T> neighbourItem = neighbourItems[i];
if (!neighbourItem.IsVisited)
{
neighbourItem.IsVisited = true;
DBSCANObject <T>[] neighbourItems2 = null;
RegionQuery(allItems, neighbourItem.ClusterItem, metricFunction, out neighbourItems2);
if (neighbourItems2.Length >= minCount)
{
neighbourItems = neighbourItems.Union(neighbourItems2).ToArray();
}
}
if (neighbourItem.ClusterId == 0)
{
neighbourItem.ClusterId = c;
}
}
}
