Voronoi diagram#
This module provides the class VoronoiDiagram for computing the
Voronoi diagram of a finite list of points in \(\RR^d\).
- class sage.geometry.voronoi_diagram.VoronoiDiagram(points)[source]#
Bases:
SageObjectBase class for the Voronoi diagram.
Compute the Voronoi diagram of a list of points.
INPUT:
points– a list of points. Any valid input for thePointConfigurationwill do.
OUTPUT:
An instance of the VoronoiDiagram class.
EXAMPLES:
Get the Voronoi diagram for some points in \(\RR^3\):
sage: V = VoronoiDiagram([[1, 3, .3], [2, -2, 1], [-1, 2, -.1]]); V The Voronoi diagram of 3 points of dimension 3 in the Real Double Field sage: VoronoiDiagram([]) The empty Voronoi diagram.
>>> from sage.all import * >>> V = VoronoiDiagram([[Integer(1), Integer(3), RealNumber('.3')], [Integer(2), -Integer(2), Integer(1)], [-Integer(1), Integer(2), -RealNumber('.1')]]); V The Voronoi diagram of 3 points of dimension 3 in the Real Double Field >>> VoronoiDiagram([]) The empty Voronoi diagram.
Get the Voronoi diagram of a regular pentagon in
AA^2. All cells meet at the origin:sage: DV = VoronoiDiagram([[AA(c) for c in v] # needs sage.rings.number_field ....: for v in polytopes.regular_polygon(5).vertices_list()]); DV The Voronoi diagram of 5 points of dimension 2 in the Algebraic Real Field sage: all(P.contains([0, 0]) for P in DV.regions().values()) # needs sage.rings.number_field True sage: any(P.interior_contains([0, 0]) for P in DV.regions().values()) # needs sage.rings.number_field False
>>> from sage.all import * >>> DV = VoronoiDiagram([[AA(c) for c in v] # needs sage.rings.number_field ... for v in polytopes.regular_polygon(Integer(5)).vertices_list()]); DV The Voronoi diagram of 5 points of dimension 2 in the Algebraic Real Field >>> all(P.contains([Integer(0), Integer(0)]) for P in DV.regions().values()) # needs sage.rings.number_field True >>> any(P.interior_contains([Integer(0), Integer(0)]) for P in DV.regions().values()) # needs sage.rings.number_field False
If the vertices are not converted to
AAbefore, the method throws an error:sage: polytopes.dodecahedron().vertices_list()[0][0].parent() # needs sage.groups sage.rings.number_field Number Field in sqrt5 with defining polynomial x^2 - 5 with sqrt5 = 2.236067977499790? sage: VoronoiDiagram(polytopes.dodecahedron().vertices_list()) # needs sage.groups sage.rings.number_field Traceback (most recent call last): ... NotImplementedError: Base ring of the Voronoi diagram must be one of QQ, RDF, AA.
>>> from sage.all import * >>> polytopes.dodecahedron().vertices_list()[Integer(0)][Integer(0)].parent() # needs sage.groups sage.rings.number_field Number Field in sqrt5 with defining polynomial x^2 - 5 with sqrt5 = 2.236067977499790? >>> VoronoiDiagram(polytopes.dodecahedron().vertices_list()) # needs sage.groups sage.rings.number_field Traceback (most recent call last): ... NotImplementedError: Base ring of the Voronoi diagram must be one of QQ, RDF, AA.
ALGORITHM:
We use hyperplanes tangent to the paraboloid one dimension higher to get a convex polyhedron and then project back to one dimension lower.
Todo
The dual construction: Delaunay triangulation
improve 2d-plotting
implement 3d-plotting
more general constructions, like Voroi diagrams with weights (power diagrams)
REFERENCES:
[Mat2002] Ch.5.7, p.118.
AUTHORS:
Moritz Firsching (2012-09-21)
- ambient_dim()[source]#
Return the ambient dimension of the points.
EXAMPLES:
sage: V = VoronoiDiagram([[.5, 3], [2, 5], [4, 5], [4, -1]]) sage: V.ambient_dim() 2 sage: V = VoronoiDiagram([[1, 2, 3, 4, 5, 6]]); V.ambient_dim() 6
>>> from sage.all import * >>> V = VoronoiDiagram([[RealNumber('.5'), Integer(3)], [Integer(2), Integer(5)], [Integer(4), Integer(5)], [Integer(4), -Integer(1)]]) >>> V.ambient_dim() 2 >>> V = VoronoiDiagram([[Integer(1), Integer(2), Integer(3), Integer(4), Integer(5), Integer(6)]]); V.ambient_dim() 6
- base_ring()[source]#
Return the base_ring of the regions of the Voronoi diagram.
EXAMPLES:
sage: V = VoronoiDiagram([[1, 3, 1], [2, -2, 1], [-1, 2, 1/2]]); V.base_ring() Rational Field sage: V = VoronoiDiagram([[1, 3.14], [2, -2/3], [-1, 22]]); V.base_ring() Real Double Field sage: V = VoronoiDiagram([[1, 3], [2, 4]]); V.base_ring() Rational Field
>>> from sage.all import * >>> V = VoronoiDiagram([[Integer(1), Integer(3), Integer(1)], [Integer(2), -Integer(2), Integer(1)], [-Integer(1), Integer(2), Integer(1)/Integer(2)]]); V.base_ring() Rational Field >>> V = VoronoiDiagram([[Integer(1), RealNumber('3.14')], [Integer(2), -Integer(2)/Integer(3)], [-Integer(1), Integer(22)]]); V.base_ring() Real Double Field >>> V = VoronoiDiagram([[Integer(1), Integer(3)], [Integer(2), Integer(4)]]); V.base_ring() Rational Field
- plot(cell_colors=None, **kwds)[source]#
Return a graphical representation for 2-dimensional Voronoi diagrams.
INPUT:
cell_colors– (default:None) provide the colors for the cells, either as dictionary. Randomly colored cells are provided withNone.**kwds– optional keyword parameters, passed on as arguments for plot().
OUTPUT:
A graphics object.
EXAMPLES:
sage: # needs sage.plot sage: P = [[0.671, 0.650], [0.258, 0.767], [0.562, 0.406], ....: [0.254, 0.709], [0.493, 0.879]] sage: V = VoronoiDiagram(P); S=V.plot() sage: show(S, xmin=0, xmax=1, ymin=0, ymax=1, aspect_ratio=1, axes=false) sage: S = V.plot(cell_colors={0: 'red', 1: 'blue', 2: 'green', ....: 3: 'white', 4: 'yellow'}) sage: show(S, xmin=0, xmax=1, ymin=0, ymax=1, aspect_ratio=1, axes=false) sage: S = V.plot(cell_colors=['red', 'blue', 'red', 'white', 'white']) sage: show(S, xmin=0, xmax=1, ymin=0, ymax=1, aspect_ratio=1, axes=false) sage: S = V.plot(cell_colors='something else') Traceback (most recent call last): ... AssertionError: 'cell_colors' must be a list or a dictionary
>>> from sage.all import * >>> # needs sage.plot >>> P = [[RealNumber('0.671'), RealNumber('0.650')], [RealNumber('0.258'), RealNumber('0.767')], [RealNumber('0.562'), RealNumber('0.406')], ... [RealNumber('0.254'), RealNumber('0.709')], [RealNumber('0.493'), RealNumber('0.879')]] >>> V = VoronoiDiagram(P); S=V.plot() >>> show(S, xmin=Integer(0), xmax=Integer(1), ymin=Integer(0), ymax=Integer(1), aspect_ratio=Integer(1), axes=false) >>> S = V.plot(cell_colors={Integer(0): 'red', Integer(1): 'blue', Integer(2): 'green', ... Integer(3): 'white', Integer(4): 'yellow'}) >>> show(S, xmin=Integer(0), xmax=Integer(1), ymin=Integer(0), ymax=Integer(1), aspect_ratio=Integer(1), axes=false) >>> S = V.plot(cell_colors=['red', 'blue', 'red', 'white', 'white']) >>> show(S, xmin=Integer(0), xmax=Integer(1), ymin=Integer(0), ymax=Integer(1), aspect_ratio=Integer(1), axes=false) >>> S = V.plot(cell_colors='something else') Traceback (most recent call last): ... AssertionError: 'cell_colors' must be a list or a dictionary
Trying to plot a Voronoi diagram of dimension other than 2 gives an error:
sage: VoronoiDiagram([[1, 2, 3], [6, 5, 4]]).plot() # needs sage.plot Traceback (most recent call last): ... NotImplementedError: Plotting of 3-dimensional Voronoi diagrams not implemented
>>> from sage.all import * >>> VoronoiDiagram([[Integer(1), Integer(2), Integer(3)], [Integer(6), Integer(5), Integer(4)]]).plot() # needs sage.plot Traceback (most recent call last): ... NotImplementedError: Plotting of 3-dimensional Voronoi diagrams not implemented
- points()[source]#
Return the input points (as a PointConfiguration).
EXAMPLES:
sage: V = VoronoiDiagram([[.5, 3], [2, 5], [4, 5], [4, -1]]); V.points() A point configuration in affine 2-space over Real Field with 53 bits of precision consisting of 4 points. The triangulations of this point configuration are assumed to be connected, not necessarily fine, not necessarily regular.
>>> from sage.all import * >>> V = VoronoiDiagram([[RealNumber('.5'), Integer(3)], [Integer(2), Integer(5)], [Integer(4), Integer(5)], [Integer(4), -Integer(1)]]); V.points() A point configuration in affine 2-space over Real Field with 53 bits of precision consisting of 4 points. The triangulations of this point configuration are assumed to be connected, not necessarily fine, not necessarily regular.
- regions()[source]#
Return the Voronoi regions of the Voronoi diagram as a dictionary of polyhedra.
EXAMPLES:
sage: V = VoronoiDiagram([[1, 3, .3], [2, -2, 1], [-1, 2, -.1]]) sage: P = V.points() sage: V.regions() == {P[0]: Polyhedron(base_ring=RDF, lines=[(-RDF(0.375), RDF(0.13888888890000001), RDF(1.5277777779999999))], ....: rays=[(RDF(9), -RDF(1), -RDF(20)), (RDF(4.5), RDF(1), -RDF(25))], ....: vertices=[(-RDF(1.1074999999999999), RDF(1.149444444), RDF(9.0138888890000004))]), ....: P[1]: Polyhedron(base_ring=RDF, lines=[(-RDF(0.375), RDF(0.13888888890000001), RDF(1.5277777779999999))], ....: rays=[(RDF(9), -RDF(1), -RDF(20)), (-RDF(2.25), -RDF(1), RDF(2.5))], ....: vertices=[(-RDF(1.1074999999999999), RDF(1.149444444), RDF(9.0138888890000004))]), ....: P[2]: Polyhedron(base_ring=RDF, lines=[(-RDF(0.375), RDF(0.13888888890000001), RDF(1.5277777779999999))], ....: rays=[(RDF(4.5), RDF(1), -RDF(25)), (-RDF(2.25), -RDF(1), RDF(2.5))], ....: vertices=[(-RDF(1.1074999999999999), RDF(1.149444444), RDF(9.0138888890000004))])} True
>>> from sage.all import * >>> V = VoronoiDiagram([[Integer(1), Integer(3), RealNumber('.3')], [Integer(2), -Integer(2), Integer(1)], [-Integer(1), Integer(2), -RealNumber('.1')]]) >>> P = V.points() >>> V.regions() == {P[Integer(0)]: Polyhedron(base_ring=RDF, lines=[(-RDF(RealNumber('0.375')), RDF(RealNumber('0.13888888890000001')), RDF(RealNumber('1.5277777779999999')))], ... rays=[(RDF(Integer(9)), -RDF(Integer(1)), -RDF(Integer(20))), (RDF(RealNumber('4.5')), RDF(Integer(1)), -RDF(Integer(25)))], ... vertices=[(-RDF(RealNumber('1.1074999999999999')), RDF(RealNumber('1.149444444')), RDF(RealNumber('9.0138888890000004')))]), ... P[Integer(1)]: Polyhedron(base_ring=RDF, lines=[(-RDF(RealNumber('0.375')), RDF(RealNumber('0.13888888890000001')), RDF(RealNumber('1.5277777779999999')))], ... rays=[(RDF(Integer(9)), -RDF(Integer(1)), -RDF(Integer(20))), (-RDF(RealNumber('2.25')), -RDF(Integer(1)), RDF(RealNumber('2.5')))], ... vertices=[(-RDF(RealNumber('1.1074999999999999')), RDF(RealNumber('1.149444444')), RDF(RealNumber('9.0138888890000004')))]), ... P[Integer(2)]: Polyhedron(base_ring=RDF, lines=[(-RDF(RealNumber('0.375')), RDF(RealNumber('0.13888888890000001')), RDF(RealNumber('1.5277777779999999')))], ... rays=[(RDF(RealNumber('4.5')), RDF(Integer(1)), -RDF(Integer(25))), (-RDF(RealNumber('2.25')), -RDF(Integer(1)), RDF(RealNumber('2.5')))], ... vertices=[(-RDF(RealNumber('1.1074999999999999')), RDF(RealNumber('1.149444444')), RDF(RealNumber('9.0138888890000004')))])} True