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onlyPlanar -- removes non-planar graphs from a list

Synopsis

Usage:

P = onlyPlanar L

P = onlyPlanar(L, non)
Inputs:
- L, a list, containing graphs in various formats
- non, a Boolean value, whether to return non-planar graphs
Outputs:
- P, a list, containing the planar graphs of $L$ in Graph6 or Sparse6 format

Description

A graph is planar if the graph can be embedded in the plane, i.e., the vertices can be arranged such that no edges cross except at vertices.

The only non-planar graph on five vertices is the complete graph.

i1 : K5 = graph flatten for i from 0 to 4 list for j from i+1 to 4 list {i,j};

i2 : P = onlyPlanar(generateGraphs 5, true)

o2 = {D~{}

o2 : List

i3 : areIsomorphic(first P, K5)

o3 = true

This method uses the program planarg. The code was written by Paulette Lieby for the Magma project and used with permission in the software nauty.

See also

isPlanar -- determines if a given graph is planar

Ways to use onlyPlanar :

onlyPlanar(List)
onlyPlanar(List,Boolean)

For the programmer

The object onlyPlanar is a method function.