/// <summary>
/// This method will add a given event to the list of events. Any previous
/// clustering information will be removed.
/// </summary>
/// <param name="evt">The event to be added</param>
public void Add(Event evt)
{
// Remove any previous clustering data
evt.Coordinate.ClearClusterData();
// Add the event to the EventCollection
Events.Add(evt);
}
/// <summary>
/// This method will return all coordinates within C's eps-neighbourhood.
/// </summary>
/// <param name="c">The centroid coordinate</param>
/// <returns>A list of neighbouring coordinates</returns>
private EventCollection GetRegion(Event evt)
{
// Collection of neighbouring coordinates
EventCollection neighbours = new EventCollection();
// Square the Epsilon (radius) to get the diameter of the neighbourhood
double eps = Epsilon * Epsilon;
// Loop over all coordinates
foreach (Event neighbour in Calls)
{
// Calculate the distance of the two coordinates
double distance = Distance.haversine(evt.Coordinate, neighbour.Coordinate);
// Class as a neighbour if it falls in the 'catchment area'
if (eps >= distance)
{
neighbours.Add(neighbour);
}
}
return neighbours;
}
/// <summary>
/// This function will expand each of the given coordinate neighbours, and
/// all of their neighbours. This will decide which coordinates are within
/// the given coordinate's EPS, and therefore whether or not the neighbours
/// belong to the new cluster.
/// </summary>
/// <param name="c">The coordinate to expand</param>
/// <param name="clusterId">The current cluster ID</param>
/// <returns>whether or not a new cluster has been defined or not</returns>
private bool ExpandCluster(Event evt, int clusterId)
{
// Get the all of evt's neighbours.
EventCollection neighbours = GetRegion(evt);
neighbours.Centroid.Radius = Epsilon;
// Remove itself from the neighbours
neighbours.Remove(evt);
// Decrement the MinPoints by one so that we take
int minimumPoints = MinPoints - 1;
// Check to see if there is a core point (based on the minimum number of points per cluster)
if (neighbours.Count < minimumPoints)
{
evt.Coordinate.Classified = true;
evt.Coordinate.Noise = true;
return false;
}
// Assume that all points are reachable from C
neighbours.UpdateAllClusterID(clusterId);
// Explore all the neighbours
while (neighbours.Count > 0)
{
// Get C's neighbour
Event currentNeighbour = neighbours[0];
// Get all the neighbours of the original neighbour
EventCollection neighbouringNeighbours = GetRegion(currentNeighbour);
if (neighbouringNeighbours.Count >= minimumPoints)
{
// Check to see if
foreach (Event resultP in neighbouringNeighbours)
{
if (!resultP.Coordinate.Classified || resultP.Coordinate.Noise)
{
if (!resultP.Coordinate.Classified)
{
resultP.Coordinate.Classified = true;
resultP.Coordinate.Noise = false;
neighbours.Add(resultP);
}
resultP.Coordinate.ClusterId = clusterId;
}
}
}
// Remove C's direct neighbour as it has been explored.
neighbours.Remove(currentNeighbour);
}
return true;
}
/// <summary>
/// This method will find a given event's closest cluster. The distance between
/// the coordinate and the cluster's centroid is calculated using the haversine
/// formula.
/// </summary>
/// <see cref="Distance.haversine"/>
/// <param name="clusters">a list of clusters</param>
/// <param name="evt">the pivot event</param>
/// <returns>index location of the cluster</returns>
private int FindNearestCluster(List<EventCollection> clusters, Event evt)
{
// The minimum distance to a coordinate
double minimumDistance = Double.MaxValue;
// The index of the nearest cluster
int clusterIndex = -1;
// Find the nearest cluster
for (int k = 0; k < clusters.Count; k++)
{
// Calculate the distance
double distance = Distance.haversine(evt.Coordinate, clusters[k].Centroid);
// Compare the two distance values
if (minimumDistance > distance)
{
// A smaller distance has been found
minimumDistance = distance;
clusterIndex = k;
}
}
return clusterIndex;
}