/// <summary>
/// Measures distance between two points
/// </summary>
public static double Dist(ClusterGame x, ClusterGame y)
{
double diffNA = y._NAsales - x._NAsales;
double diffEU = y._EUsales - x._EUsales;
return(diffNA * diffNA + diffEU * diffEU);
}
/// <summary>
/// Returns list of points in selected region around the specified point
/// </summary>
private static List <ClusterGame> GetNeighbours(List <ClusterGame> points, ClusterGame p, double region)
{
List <ClusterGame> reg = new List <ClusterGame>();
for (int i = 0; i < points.Count; i++)
{
double dist = Dist(p, points[i]);
if (dist <= region)
{
reg.Add(points[i]);
}
}
return(reg);
}
/// <summary>
/// DBSCAN clustering function on the list of points
/// </summary>
private static List <List <ClusterGame> > StartClustering(List <ClusterGame> points, double region, int min_points)
{
region = square(region);
int ClstId = 1;
if (points == null)
{
return(null);
}
List <List <ClusterGame> > clusters = new List <List <ClusterGame> >();
for (int counter = 0; counter < points.Count; counter++)
{
ClusterGame p = points[counter];
if (p._cluster == ClusterGame._checked)
{
if (CheckCluster(points, p, ClstId, region, min_points))
{
ClstId++;
}
}
}
// Assign point to clusters
int max = points.OrderBy
(p => p._cluster).Last()._cluster;
if (max < 1)
{
return(clusters);
}
for (int i = 0; i < max; i++)
{
clusters.Add(new List <ClusterGame>());
}
foreach (ClusterGame p in points)
{
if (p._cluster > 0)
{
clusters[p._cluster - 1].Add(p);
}
}
return(clusters);
}
/// <summary>
/// Check if the cluster can be expanded
/// </summary>
private static bool CheckCluster(List <ClusterGame> points, ClusterGame p, int clusterId, double region, int min_points)
{
List <ClusterGame> neighboursList = GetNeighbours(points, p, region);
// mark point as NOISE if the count of neighbours is bellow treshold
if (neighboursList.Count < min_points)
{
MarkNoise(p);
return(false);
}
//Expand cluster if the count of neighbours is above treshold
else
{
//Remove points from the list
for (int i = 0; i < neighboursList.Count; i++)
{
neighboursList[i]._cluster = clusterId;
}
neighboursList.Remove(p);
//Repeat for every neighbour point
while (neighboursList.Count > 0)
{
ClusterGame current = neighboursList[0];
List <ClusterGame> result = GetNeighbours(points, current, region);
if (result.Count >= min_points)
{
for (int i = 0; i < result.Count; i++)
{
ClusterGame res = result[i];
if (res._cluster == ClusterGame._checked ||
res._cluster == ClusterGame._isnoise)
{
if (res._cluster == ClusterGame._checked)
{
neighboursList.Add(res);
}
res._cluster = clusterId;
}
}
}
neighboursList.Remove(current);
}
return(true);
}
}
private static void MarkNoise(ClusterGame p)
{
p._cluster = ClusterGame._isnoise;
}
/// <summary>
/// Returns cluster with the biggest amount of point aka best candidate
/// </summary>
private static List <ClusterGame> BestCluster(List <ClusterGame> points, double maxDiameter)
{
double diametersqrd = maxDiameter * maxDiameter;
List <List <ClusterGame> > c = new List <List <ClusterGame> >();
List <ClusterGame> cc = null;
int[] candidateNumbers = new int[points.Count];
int totalPointsAllocated = 0;
int currentCandidateNumber = 0;
for (int i = 0; i < points.Count; i++)
{
if (totalPointsAllocated == points.Count)
{
break;
}
if (candidateNumbers[i] > 0)
{
continue;
}
currentCandidateNumber++;
cc = new List <ClusterGame>();
cc.Add(points[i]);
candidateNumbers[i] = currentCandidateNumber;
totalPointsAllocated++;
ClusterGame latestPoint = points[i];
double[] diametersSquared = new double[points.Count];
while (true)
{
if (totalPointsAllocated == points.Count)
{
break;
}
int closest = -1;
double minDiameterSquared = Int32.MaxValue;
for (int j = i + 1; j < points.Count; j++)
{
if (candidateNumbers[j] > 0)
{
continue;
}
double distSquared = Dist(latestPoint, points[j]);
if (distSquared > diametersSquared[j])
{
diametersSquared[j] = distSquared;
}
if (diametersSquared[j] < minDiameterSquared)
{
minDiameterSquared = diametersSquared[j];
closest = j;
}
}
if ((double)minDiameterSquared <= diametersqrd)
{
cc.Add(points[closest]);
candidateNumbers[closest] = currentCandidateNumber;
totalPointsAllocated++;
}
else
{
break;
}
}
c.Add(cc);
}
int maxPoints = -1;
int bestCandidateNumber = 0;
for (int i = 0; i < c.Count; i++)
{
if (c[i].Count > maxPoints)
{
maxPoints = c[i].Count;
bestCandidateNumber = i + 1;
}
}
for (int i = candidateNumbers.Length - 1; i >= 0; i--)
{
if (candidateNumbers[i] == bestCandidateNumber)
{
points.RemoveAt(i);
}
}
return(c[bestCandidateNumber - 1]);
}