internal void BuildTree(List<VectorData> points)
{
if (!points.Any())
{
return;
}
DimensionCount = points.First().Data.Count();
root = GenerateNode(0, points, 0, points.Count() - 1);
}
void FindPointsWithinRadius(KDNode node, VectorData targetPoint, List<VectorData> result, double radius)
{
if (node.Values != targetPoint)
{
TryToSaveRadius(node, targetPoint, result, radius);
}
var dMinus1 = node.Dimension - 1;
if (dMinus1 < 0)
{
dMinus1 = DimensionCount - 1;
}
var perpendicularDistance = Math.Abs(node.Values.Data.Skip(node.Dimension).First() - targetPoint.Data.Skip(dMinus1).First());
if (perpendicularDistance < radius || node.Values == targetPoint)
{
if (node.Above != null)
{
FindPointsWithinRadius(node.Above, targetPoint, result, radius);
}
if (node.Below != null)
{
FindPointsWithinRadius(node.Below, targetPoint, result, radius);
}
}
else
{
if (targetPoint.Data.Skip(dMinus1).First() < node.Values.Data.Skip(node.Dimension).First())
{
if (node.Below != null)
{
FindPointsWithinRadius(node.Below, targetPoint, result, radius);
}
}
else
{
if (node.Above != null)
{
FindPointsWithinRadius(node.Above, targetPoint, result, radius);
}
}
}
}
void TryToSaveRadius(KDNode node, VectorData target, List<VectorData> result, double radius)
{
if (node == null)
{
return;
}
var distance = AbstractDistanceFunction.CalculateDistance(target, node.Values);
if (radius < distance)
{
return;
}
result.Add(node.Values);
}
void TryToSaveRadiusWithDistance(KDNode node, VectorData target, List<KNNPoint> result, double radius)
{
if (node == null)
{
return;
}
double distance = AbstractDistanceFunction.CalculateDistance(target, node.Values);
if (radius < distance)
{
return;
}
result.Add(new KNNPoint(node.Values, distance));
}
KDNode GenerateNode(int currentD, List<VectorData> points, int left, int right)
{
if (right < left)
{
return null;
}
if (right == left)
{
return new KDNode(points[left], currentD);
}
var m = (right - left) / 2;
var medianNode = RandomizedSelect(points, m, left, right, currentD);
var node = new KDNode(medianNode, currentD);
currentD++;
if (currentD == DimensionCount)
{
currentD = 0;
}
node.Below = GenerateNode(currentD, points, left, left + m - 1);
node.Above = GenerateNode(currentD, points, left + m + 1, right);
return node;
}