public BallTreeNode(PointSet Points)
{
//if there is only a single point, set this as the data
if (Points.Count == 1)
{
Point = Points[0];
}
else
{
//Find the dimension of greatest spread
var minMax = Points.GetMinMaxWeights();
double maxSpread = double.MinValue;
int maxDim = 0;
for (int d = 0; d < Points.Dimensions; d++)
{
double range = minMax.Max[d] - minMax.Min[d];
if (range > maxSpread)
{
maxSpread = d;
maxSpread = range;
}
}
PivotDim = maxDim;
//Pivot Select, Replace with QuickSelect
double[] pivots = new double[Points.Count];
for (int i = 0; i < Points.Count; i++)
{
pivots[i] = Points[i][PivotDim];
}
Array.Sort(pivots);
double pivotValue = pivots[(Points.Count - 1) / 2];
//Create left and right children
List <KPoint> left = new List <KPoint>();
List <KPoint> right = new List <KPoint>();
for (int i = 0; i < Points.Count; i++)
{
if (Points[i][PivotDim] <= pivotValue)
{
left.Add(Points[i]);
}
else
{
right.Add(Points[i]);
}
}
leftNode = new BallTreeNode(new PointSet(left));
rightNode = new BallTreeNode(new PointSet(right));
}
}
public MinHeapPriorityQueue <KPoint> NearestNeighbors(KPoint p, int k, MinHeapPriorityQueue <KPoint> Q, BallTreeNode B)
{
if (p[B.PivotDim] > Q.peek().elucideanDistance(p))
{
return(Q);
}
else if (B.IsLeaf())
{
if (p.elucideanDistance(B.Point) < p.elucideanDistance(Q.peek()))
{
if (Q.Count >= k)
{
Q.extractMin();
}
}
}
return(Q);
}
