G&G Graph LibraryLast update=30 May, 2018
A number of graph files are available via ftp. See also the G&G overview, where pictures of many of these graphs are shown. If you have interesting graphs/digraphs/groups, please consider posting them on this website. Examples are strongly regular graphs, distance regular graphs, incidence graphs of finite geometries or BIBDs, catalogs of cubic graphs, quartic graphs, torus maps, transitive graphs, etc. Send them by e-mail, together with any additional information that may be useful.
The "Draw Symmetric" command in G&G can be used to produce interesting drawings of graphs. Click for an example illustrating 4 very different-looking symmetric views of Q4, the 4-cube.
G&G text format for graphs
Graphs are stored in the G&G ascii format. The graph of the cube is used as an example.
120 64 327 256
-1 2 4 5
-2 3 6
-3 4 7
-5 6 8
The $ symbol is used to separate graphs stored in a single file. The second line indicates that a graph follows. The third line is the name of the graph. The fourth line is the number n of vertices. The vertices are numbered 1..n. The fifth line is the bounding rectangle of the window in which the graph is drawn. Then vertex 1 is indicated by -1. Its adjacent points follow. Vertex 2 is indicated by -2, then its adjacent points, etc. The end of the list is indicated by 0.
Graphs in this format are very easily input.
The graph adjacencies can be followed by the (h,v)-coordinates of the vertices. These are the horizontal and vertical offsets from the top left corner of the window. For the example above, coordinates appear as follows.&Coordinates
-1 211 14
-2 301 14
-3 301 89
-4 211 89
-5 146 74
-6 236 74
-7 236 149
-8 146 149
Additional optional information can also be included, such as the colour of the vertices, and a renaming of the points. Save some graphs in text format using G&G to see the format used.
Note: Some files were lost as a result of a disk crash in March, 2018. They are being regenerated.
The Platonic polyhedra (updated May 1/18)
Some non-hamiltonian graphs (updated May 1/18)