Description of icosahedron

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icosahedron

PURPOSE

icosahedron(g) --- overwrite g with the icosahedron graph

SYNOPSIS

function icosahedron(g)

DESCRIPTION

 icosahedron(g) --- overwrite g with the icosahedron graph

CROSS-REFERENCE INFORMATION

This function calls:

• add add --- add edge(s) to the graph
• clear_edges clear_edges(g) --- delete all edges of g
• embed embed --- create an embedding for a graph
• full full(g) --- convert internal storage for g to full
• resize resize(g,n) --- change the number of vertices in g to n

This function is called by:

SOURCE CODE

0001 function icosahedron(g)
0002 % icosahedron(g) --- overwrite g with the icosahedron graph
0003 
0004 resize(g,12);
0005 clear_edges(g);
0006 full(g);
0007 
0008 elist = [
0009     1   2
0010     1   3
0011     1   4
0012     1   5
0013     1   9
0014     2   3
0015     2   5
0016     2   6
0017     2   7
0018     3   7
0019     3   8
0020     3   9
0021     4   5
0022     4   9
0023     4   10
0024     4   12
0025     5   6
0026     5   10
0027     6   7
0028     6   10
0029     6   11
0030     7   8
0031     7   11
0032     8   9
0033     8   11
0034     8   12
0035     9   12
0036     10  11
0037     10  12
0038     11  12
0039     ];
0040 add(g,elist);
0041 
0042 t0 = 0;
0043 t1 = -2*pi/3;
0044 t2 = 2*t1;
0045 
0046 outer = [
0047     sin(t0)     cos(t0)
0048     sin(t1)     cos(t1)
0049     sin(t2)     cos(t2)
0050     ];
0051 
0052 hex = [];
0053 
0054 for k=0:5
0055     hex = [hex; sin(-k*pi/3), cos(-k*pi/3)];
0056 end
0057 
0058 inner = outer*[cos(pi/3), sin(pi/3); -sin(pi/3), cos(pi/3)];
0059 
0060 
0061 xy = [3*outer; hex; inner/3];
0062 embed(g,xy)
0063 
0064     
0065

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