MaplePrimes - Questions and Posts tagged with graphtheory

Does there exist a regular graph of degree 4

Markiyan Hirnyk — Sun, 17 Mar 2013 07:32:53 Z

having its diameter equal to three and its number of vertices equal to 32? Is it possible to find the one with Maple? The simpleminded approach
>with(GraphTheory):
>with(RandomGraphs):
> G := RandomRegularGraph(32, 4);
> Diameter(G);
produces 4 or 5.
What I know is http://www-ma4.upc.es/~comellas/delta-d/desc_g/desc_g3.html ( the second graph).

CopyGraph and normal assignment

Petra Heijnen — Thu, 28 Feb 2013 11:10:04 Z

I've found a fundamental difference in the use of

G2:=CopyGraph(G):
and
G2:=G:

where G is a Graph in the GraphTheory package.

If I change G2 in the first case, G remains the same.

If I change G2 in the second case, G changes together with G2.

(The same happens when G is an input parameter in a procedure. Normally formal parameters cannot be changed, but if G is a graph there is no error message when changing G).

Who's number 1?

Markiyan Hirnyk — Tue, 04 Dec 2012 08:45:56 Z

I would like to pay attention to http://www.ams.org/samplings/feature-column/fc-2012-12, where a discrete analog of vector calculus on graphs is applied to rankings. In my opinion, it would be useful to implement that in the GraphTheory package. ...

External Library libgraphtheory.so could not be found/used

dadexix86 — Fri, 06 Jul 2012 10:41:34 Z

Hi!

I've got this annoying problem and it's quite simple reproducible.

> with(GraphTheory): G := Graph({{a, b}, {b, c}, {c, d}}); Edges(G);

Edges(G) returns me

Error, (in EdgesExt) external library libgraphtheory.so could not be found/used

It's the first time I encounter such a problem and have no idea on how to solve it, any advice?

I can see that libgraphtheory.so...

MRB constant Z

Marvin Ray Burns — Sat, 26 May 2012 16:42:33 Z

The MRB constant Z will probably have several parts.

The following example is from the Maple help pages
> with(GraphTheory);
> with(SpecialGraphs);
> H := HypercubeGraph(3);

DrawGraph(H)

Download May262012.mw

The number of all triangles of a graph

Markiyan Hirnyk — Sat, 10 Mar 2012 09:00:18 Z

Let G be an undirected graph having the vertices V={1,...,n}. A subset {i,j,k} is said to be a triangle of G if the complete graph with these vertices is a subgraph of G.
How to find the number of all triangles of G in an optimal way? The code should work with RandomGraph(400,1000).

GraphTheory - tree structure issues

Christopher2222 — Fri, 07 Oct 2011 20:44:25 Z

Using the tree structure example from ?GraphTheory[DrawGraph] using showlabels=true the highlighted areas are merged and no amount of zooming can seperate the merged yellow areas.

Another issue, I don't see the advantage of style=tree when a tree structure can only be printed if the original DrawGraph is already represented as a tree style structure when...

A list of small graphs, invariants and conjectured inequalites

Mon, 29 Aug 2011 15:30:44 Z

A list of small graphs with associated pictures and tables of
values of various graph invariants.

The graph invariants were made using Maple programs which uses
the networks and GraphTheory packages.

A picture presents some inequality conjectures between the graph invariants.

http://www.msci.memphis.edu/~speeds/

Sam Speed August 29, 2011

How can I make multi-graphs?

lukegeo — Fri, 22 Apr 2011 16:03:30 Z

Hi! I have been searching the forum, but with no luck. How do I get maple to handle graphs with multiple edges between vertices? I can't seem to find a function for this. Does one exist? I tried to do this by coloring the edges, but they just get re-colored.

EE1:=[1, 2], [3, 1], [2, 3], [4, 5], [6, 4], [5, 6], [7, 8], [9, 7], [8, 9];
EE2:=[2, 3], [4, 2], [3, 4], [5, 6], [7, 5], [6, 7], [1, 8], [9, 1], [8, 9];
EE3:=[3, 4], [5, 3], [4, 5], [6, 7...

Attributes in graphs and AddVertex

djordan99 — Sat, 26 Mar 2011 20:35:43 Z

The AddVertex command (in GraphTheory) does not seem to copy any attributes that were set in the original graph.

with(GraphTheory):
G := CompleteGraph(5):
SetGraphAttribute(G,"graphAtt" = 1);
SetVertexAttribute(G,1,"vertexAtt" = 1);
SetEdgeAttribute(G,{1,2},"edgeAtt" = 1);
H := AddVertex(G,6):
GetGraphAttribute(H,"graphAtt");
...

Digraph arrow placement

djordan99 — Sat, 19 Feb 2011 20:38:53 Z

Does anyone know how to control the placement of the directional arrows for a digraph?

Here's an example:

with(GraphTheory):

G := Digraph(Trail(4,2,1,3,4,5),Trail(6,8,9,7,6,5));

SetVertexPositions(G,[[0,1],[1,1],[0,0],[1,0],[2,0],[3,0],[4,0],[3,1],[4,1]]);

DrawGraph(G);

produces:

The...

Why is this graph not a network?

djordan99 — Sun, 06 Feb 2011 20:31:20 Z

Can anyone help me understand why the following happens?

N := GraphTheory[Digraph]({[1,3],[3,9],[9,27]});

GraphTheory[IsNetwork](N);

and

M := GraphTheory[Digraph]({[1,2],[2,4],[4,8]});

GraphTheory[IsNetwork](M);

both indicate that the graph is not a network. On the other hand, for numbers n other than 2 and 3, Maple does recognize the graph {[1,n],[n,n^2],[n^2,n^3]} as a network.

This procedure that I wrote:

Incomplete Quoted Name error when using Terminal.

liambaird — Tue, 16 Nov 2010 18:41:52 Z

Hey,

I've been running the following program in a maple worksheet and it has worked fine.

Now I want to run it on an Ubuntu machine that has some extra computing power to get through a big data set.

However I get strange "Incomplete Quoted Name" errors, even when I have no quoted names in my input at all.

This is just alittle bit of the output I'm getting:

|\^/| Maple 14 (X86 64 LINUX)
._|\| |/|_. Copyright (c...

Graph Theory-:NonIsomorphicGraphs help

daniel233 — Mon, 14 Jun 2010 16:37:00 Z

Hey everyone,

I've been using nonisomorphicgraphs for a while now, and my professor would really like to know if there is a pattern in the order in which it spits out the graphs. I've noticed that they pair them up in complements of each other(or as close as possible), but has anyone found the order in which they come out, and what the reason for this order is?