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51 lines
1.7 KiB
Go
51 lines
1.7 KiB
Go
// Copyright ©2019 The Gonum Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package kdtree
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var (
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_ Interface = nbPoints{}
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_ Comparable = nbPoint{}
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)
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// nbRandoms is the maximum number of random values to sample for calculation of median of
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// random elements.
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var nbRandoms = 100
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// nbPoint represents a point in a k-d space that satisfies the Comparable interface.
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type nbPoint Point
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func (p nbPoint) Compare(c Comparable, d Dim) float64 { q := c.(nbPoint); return p[d] - q[d] }
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func (p nbPoint) Dims() int { return len(p) }
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func (p nbPoint) Distance(c Comparable) float64 {
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q := c.(nbPoint)
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var sum float64
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for dim, c := range p {
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d := c - q[dim]
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sum += d * d
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}
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return sum
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}
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// nbPoints is a collection of point values that satisfies the Interface.
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type nbPoints []nbPoint
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func (p nbPoints) Index(i int) Comparable { return p[i] }
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func (p nbPoints) Len() int { return len(p) }
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func (p nbPoints) Pivot(d Dim) int { return nbPlane{nbPoints: p, Dim: d}.Pivot() }
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func (p nbPoints) Slice(start, end int) Interface { return p[start:end] }
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// nbPlane is a wrapping type that allows a Points type be pivoted on a dimension.
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type nbPlane struct {
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Dim
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nbPoints
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}
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func (p nbPlane) Less(i, j int) bool { return p.nbPoints[i][p.Dim] < p.nbPoints[j][p.Dim] }
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func (p nbPlane) Pivot() int { return Partition(p, MedianOfRandoms(p, nbRandoms)) }
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func (p nbPlane) Slice(start, end int) SortSlicer { p.nbPoints = p.nbPoints[start:end]; return p }
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func (p nbPlane) Swap(i, j int) {
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p.nbPoints[i], p.nbPoints[j] = p.nbPoints[j], p.nbPoints[i]
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}
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