Documentation
¶
Overview ¶
Package kdtree implements a k-d tree.
Index ¶
- Variables
- func MedianOfMedians(list SortSlicer) int
- func MedianOfRandoms(list SortSlicer, n int) int
- func Partition(list sort.Interface, pivot int) int
- func Select(list SortSlicer, k int) int
- type Bounder
- type Bounding
- type Comparable
- type ComparableDist
- type Dim
- type DistKeeper
- type Extender
- type Heap
- type Interface
- type Keeper
- type NKeeper
- type Node
- type Operation
- type Plane
- type Point
- type Points
- type SortSlicer
- type Tree
- func (t *Tree) Contains(c Comparable) bool
- func (t *Tree) Do(fn Operation) bool
- func (t *Tree) DoBounded(fn Operation, b *Bounding) bool
- func (t *Tree) Insert(c Comparable, bounding bool)
- func (t *Tree) Len() int
- func (t *Tree) Nearest(q Comparable) (Comparable, float64)
- func (t *Tree) NearestSet(k Keeper, q Comparable)
Constants ¶
This section is empty.
Variables ¶
var Randoms = 100
Randoms is the maximum number of random values to sample for calculation of median of random elements.
Functions ¶
func MedianOfMedians ¶
func MedianOfMedians(list SortSlicer) int
MedianOfMedians returns the index to the median value of the medians of groups of 5 consecutive elements.
func MedianOfRandoms ¶
func MedianOfRandoms(list SortSlicer, n int) int
MedianOfRandoms returns the index to the median value of up to n randomly chosen elements in list.
func Partition ¶
Partition partitions list such that all elements less than the value at pivot prior to the call are placed before that element and all elements greater than that value are placed after it. The final location of the element at pivot prior to the call is returned.
func Select ¶
func Select(list SortSlicer, k int) int
Select partitions list such that all elements less than the kth largest element are placed placed before k in the resulting list and all elements greater than it are placed after the position k.
Types ¶
type Bounder ¶
type Bounder interface {
Bounds() *Bounding
}
An Bounder returns a bounding volume containing the list of points. Bounds may return nil.
type Bounding ¶
type Bounding [2]Comparable
A Bounding represents a volume bounding box.
func (*Bounding) Contains ¶
func (b *Bounding) Contains(c Comparable) bool
Contains returns whether c is within the volume of the Bounding. A nil Bounding returns true.
type Comparable ¶
type Comparable interface {
// Compare returns the shortest translation of the plane through b with
// normal vector along dimension d to the parallel plane through a.
//
// Given c = a.Compare(b, d):
// c = a_d - b_d
//
Compare(Comparable, Dim) float64
// Dims returns the number of dimensions described in the Comparable.
Dims() int
// Distance returns the squared Euclidean distance between the receiver and
// the parameter.
Distance(Comparable) float64
}
A Comparable is the element interface for values stored in a k-d tree.
type ComparableDist ¶
type ComparableDist struct {
Comparable Comparable
Dist float64
}
ComparableDist holds a Comparable and a distance to a specific query. A nil Comparable is used to mark the end of the heap, so clients should not store nil values except for this purpose.
type DistKeeper ¶
type DistKeeper struct {
Heap
}
DistKeeper is a Keeper that retains the ComparableDists within the specified distance of the query that it is called to Keep.
func NewDistKeeper ¶
func NewDistKeeper(d float64) *DistKeeper
NewDistKeeper returns an DistKeeper with the max value of the heap set to d.
func (*DistKeeper) Keep ¶
func (k *DistKeeper) Keep(c ComparableDist)
Keep adds c to the heap if its distance is less than or equal to the max value of the heap.
type Extender ¶
type Extender interface {
Comparable
// Extend returns a bounding box that has been extended to include the
// receiver. Extend may return nil.
Extend(*Bounding) *Bounding
}
An Extender is a Comparable that can increase a bounding volume to include the point represented by the Comparable.
type Heap ¶
type Heap []ComparableDist
Heap is a max heap sorted on Dist.
func (*Heap) Max ¶
func (h *Heap) Max() ComparableDist
type Interface ¶
type Interface interface {
// Index returns the ith element of the list of points.
Index(i int) Comparable
// Len returns the length of the list.
Len() int
// Pivot partitions the list based on the dimension specified.
Pivot(Dim) int
// Slice returns a slice of the list.
Slice(start, end int) Interface
}
type Keeper ¶
type Keeper interface {
Keep(ComparableDist) // Keep conditionally pushes the provided ComparableDist onto the heap.
Max() ComparableDist // Max returns the maximum element of the Keeper.
heap.Interface
}
Keeper implements a conditional max heap sorted on the Dist field of the ComparableDist type. kd search is guided by the distance stored in the max value of the heap.
type NKeeper ¶
type NKeeper struct {
Heap
}
NKeeper is a Keeper that retains the n best ComparableDists that it is called to Keep.
func NewNKeeper ¶
NewNKeeper returns an NKeeper with the max value of the heap set to infinite distance. The returned NKeeper is able to retain at most n values.
func (*NKeeper) Keep ¶
func (k *NKeeper) Keep(c ComparableDist)
Keep add c to the heap if its distance is less than the maximum value of the heap. If adding c would increase the size of the heap beyond the initial maximum length, the maximum value of the heap is dropped.
type Node ¶
type Node struct {
Point Comparable
Plane Dim
Left, Right *Node
*Bounding
}
A Node holds a single point value in a k-d tree.
type Operation ¶
type Operation func(Comparable, *Bounding, int) (done bool)
An Operation is a function that operates on a Comparable. The bounding volume and tree depth of the point is also provided. If done is returned true, the Operation is indicating that no further work needs to be done and so the Do function should traverse no further.
type Plane ¶
A Plane is a wrapping type that allows a Points type be pivoted on a dimension.
func (Plane) Slice ¶
func (p Plane) Slice(start, end int) SortSlicer
type Point ¶
type Point []float64
A Point represents a point in a k-d space that satisfies the Comparable interface.
func (Point) Compare ¶
func (p Point) Compare(c Comparable, d Dim) float64
func (Point) Distance ¶
func (p Point) Distance(c Comparable) float64
type Points ¶
type Points []Point
A Points is a collection of point values that satisfies the Interface.
func (Points) Index ¶
func (p Points) Index(i int) Comparable
type SortSlicer ¶
type SortSlicer interface {
sort.Interface
Slice(start, end int) SortSlicer
}
A SortSlicer satisfies the sort.Interface and is able to slice itself.
type Tree ¶
A Tree implements a k-d tree creation and nearest neighbour search.
func New ¶
New returns a k-d tree constructed from the values in p. If p is a Bounder and bounding is true, bounds are determined for each node.
func (*Tree) Contains ¶
func (t *Tree) Contains(c Comparable) bool
Contains returns whether a Comparable is in the bounds of the tree. If no bounding has been constructed Contains returns true.
func (*Tree) Do ¶
Do performs fn on all values stored in the tree. A boolean is returned indicating whether the Do traversal was interrupted by an Operation returning true. If fn alters stored values' sort relationships, future tree operation behaviors are undefined.
func (*Tree) DoBounded ¶
DoBounded performs fn on all values stored in the tree that are within the specified bound. If b is nil, the result is the same as a Do. A boolean is returned indicating whether the DoBounded traversal was interrupted by an Operation returning true. If fn alters stored values' sort relationships future tree operation behaviors are undefined.
func (*Tree) Insert ¶
func (t *Tree) Insert(c Comparable, bounding bool)
Insert adds a point to the tree, updating the bounding volumes if bounding is true, and the tree is empty or the tree already has bounding volumes stored, and c is an Extender. No rebalancing of the tree is performed.
func (*Tree) Nearest ¶
func (t *Tree) Nearest(q Comparable) (Comparable, float64)
Nearest returns the nearest value to the query and the distance between them.
func (*Tree) NearestSet ¶
func (t *Tree) NearestSet(k Keeper, q Comparable)
NearestSet finds the nearest values to the query accepted by the provided Keeper, k. k must be able to return a ComparableDist specifying the maximum acceptable distance when Max() is called, and retains the results of the search in min sorted order after the call to NearestSet returns.
Source Files