Converting polygon to graph in V7

Question

I've unsuccessfully tried many ways of converting polygon points into a graph using Mathematica 7, and I am frustrated. I looked at this post, but it doesn't work:

Needs["Combinatorica`"];
crds = {{1, 10}, {2, 4}, {10, 5}, {20, 10}};
vertices = Range[Length[crds]];
edges = Thread[vertices \[DirectedEdge] RotateLeft[vertices]];

Graph[vertices, edges]

produces errors:

Syntax::sntxf: "\!\(\*StyleBox[\"\\\"\\\\\\\"\\\"\", \"MT\"]\)\!\(\*StyleBox[\!
\(vertices\), \"MT\"]\)\!\(\*StyleBox[\"\\\"\\\\\\\" cannot be followed by \\\\\\\"
\\\"\", \"MT\"]\)\!\(\*StyleBox[\!\(\(\(\\[ DirectedEdge]\)\) \(\(RotateLeft[vertices]
\)\)\), \"MT\"]\)\!\(\*StyleBox[\"\\\"\\\\\\\".\\\"\", \"MT\"]\)\!\(\*StyleBox[\!
\(\"\"\), \"MT\"]\)"

Syntax::tsntxi: "\!\(\*StyleBox[\"\\\"\\\\\\\"\\\"\", \"MT\"]\)\!\(\*StyleBox[\!\(\\[ 
DirectedEdge]\), \"MT\"]\)\!\(\*StyleBox[\"\\\"\\\\\\\" is incomplete; more input is 
needed.\\\"\", \"MT\"]\)\!\(\*StyleBox[\!\(\"\"\), \"MT\"]\)"

Syntax::sntxi: Incomplete expression; more input is needed.

Any ideas?

Answer 1

With Combinatorica, you should usually use MakeGraph rather than Graph directly. Here are some expressions that create the graph you want and which can be easily adapted for use with any graph that you've defined appropriate vertices and edges symbols for:

Needs["Combinatorica`"]
crds = {{1, 10}, {2, 4}, {10, 5}, {20, 10}};
vertices = Range[Length[crds]];
edges = Thread[vertices -> RotateLeft[vertices]];
g = MakeGraph[vertices, MemberQ[edges, #1 -> #2] &]
ShowGraph@g

Answer 2

Needs["Combinatorica`"];
crds = {{1, 10}, {2, 4}, {10, 5}, {20, 10}}
vertices = Range[Length[crds]]; edges = 
Thread[vertices -> RotateLeft[vertices]];
GraphPlot[edges]