VORONOI_PLOT
Plot Voronoi Neighborhoods

VORONOI_PLOT is a MATLAB program which plots the Voronoi neighborhoods of a set of center points.

The picture is created using discrete pixel geometry, rather than sophisticated analysis. In other words, each center point is assigned a color at random. Then each pixel in the image is colored the same as the nearest center point.

The program allows the user to choose the values of M and N, the number of rows and columns used in the pixel array.

The program allows the user to choose the LP norm in which distances are calculated, with P any positive real value. In particular

• 1: distance = sum of absolute values of differences;
• 2: distance = square root of sum of squares of differences;
• P: distance = P-th root of sum of absolute values of P-th powers of differences;
• Inf: distance = maximum of absolute values of differences;

Usage:

voronoi_plot ( xy, m, n, p )

• xy is the (2,NC) array of center points.
• m is the number of rows in the pixel image;
• n is the number of columns in the pixel image;
• p chooses the P-norm (1, 2, Inf, or some positive real value).

Licensing:

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Languages:

VORONOI_PLOT is available in a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

SPHERE_DELAUNAY, a MATLAB program which computes the Delaunay triangulation of points on a sphere.

SPHERE_VORONOI, a MATLAB program which computes the Voronoi diagram of points on a sphere.

VORONOI_MOUNTAINS, a MATLAB program which makes a "mountain plot" of a Voronoi diagram, that is, a surface plot of the distance from each point to its nearest Voronoi generator.

Reference:

1. Franz Aurenhammer,
   Voronoi diagrams - a study of a fundamental geometric data structure,
   ACM Computing Surveys,
   Volume 23, Number 3, pages 345-405, September 1991.
2. Herbert Edelsbrunner,
   Geometry and Topology for Mesh Generation,
   Cambridge, 2001,
   QA377.E36,
   ISBN 0-521-79309-2.
3. Joseph O'Rourke,
   Computational Geometry,
   Cambridge University Press,
   Second Edition, 1998,
   QA448.D38.

Source Code:

• voronoi_plot.m, the source code.

Examples and Tests:

DIAMOND_02_00009 is a set of 9 points whose Voronoi diagram includes a "diamond" shaped region.

• diamond_02_00009.txt, the 9 points.
• diamond_02_00009_l0.25.png, a PNG image of the L0.25 neighborhoods.
• diamond_02_00009_l0.5.png, a PNG image of the L0.5 neighborhoods.
• diamond_02_00009_l1.png, a PNG image of the L1 neighborhoods.
• diamond_02_00009_l2.png, a PNG image of the L2 neighborhoods.
• diamond_02_00009_l3.png, a PNG image of the L3 neighborhoods.
• diamond_02_00009_linf.png, a PNG image of the LInfinity neighborhoods.

UNIFORM_02_00010 is a set of 10 points chosen "randomly".

• uniform_02_00010.txt, 10 "random" points in the unit square.
• uniform_02_00010_l1.png, a PNG image of the L1 neighborhoods.
• uniform_02_00010_l2.png, a PNG image of the L2 neighborhoods.
• uniform_02_00010_l3.png, a PNG image of the L3 neighborhoods.
• uniform_02_00010_l4.png, a PNG image of the L4 neighborhoods.
• uniform_02_00010_linf.png, a PNG image of the LInfinity neighborhoods.

You can go up one level to the MATLAB source codes.