Description of random_planar

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random_planar

PURPOSE

random_planar(g,n) --- create a random planar triangulation

SYNOPSIS

function random_planar(g,n)

DESCRIPTION

 random_planar(g,n) --- create a random planar triangulation
 This does NOT create a random "uniform" triangulation. Rather, it places
 n points at random in the plane and builds the Delaunay triangulation
 thereon.

CROSS-REFERENCE INFORMATION

This function calls:

• add add --- add edge(s) to the graph
• edges edges(g) --- list the edges in g as a 2-column matrix
• embed embed --- create an embedding for a graph
• resize resize(g,n) --- change the number of vertices in g to n
• size size(g) --- returns [nv,ne] for the graph

This function is called by:

SOURCE CODE

0001 function random_planar(g,n)
0002 % random_planar(g,n) --- create a random planar triangulation
0003 % This does NOT create a random "uniform" triangulation. Rather, it places
0004 % n points at random in the plane and builds the Delaunay triangulation
0005 % thereon.
0006 
0007 xy = rand(n,2)*sqrt(n);
0008 resize(g,0)
0009 resize(g,n)
0010 embed(g,xy)
0011 
0012 triangles = delaunay(xy(:,1), xy(:,2));
0013 nt = size(triangles,1);
0014 
0015 edges = [triangles(:,1:2); triangles(:,2:3); triangles(:,[1,3])];
0016 edges = sortrows(edges);
0017 edges = unique(edges,'rows');
0018 add(g,edges)

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