isRigid -- checks if a graph is rigid

Synopsis

Usage:

r = isRigid G
Inputs:
- G, a graph,
Outputs:
- r, a Boolean value,

Description

A drawing of a graph is rigid in the plane if any continuous motion of the vertices that preserve edge lengths must preserve the distance between every pair of vertices. A graph is generically rigid if any drawing of the graph with vertices in general position is rigid. This method uses Laman's Theorem to determine if a graph is rigid or not.

i1 : G = cycleGraph 4;

i2 : isRigid G

o2 = false

i3 : G' = addEdges' (G, {{1,1},{3,1}})

o3 = Graph{0 => {1, 3}      }
           1 => {0, 1, 2, 3}
           2 => {1, 3}
           3 => {0, 1, 2}

o3 : Graph

i4 : isRigid G'

o4 = true

Ways to use isRigid :

isRigid(Graph)

For the programmer

The object isRigid is a method function.