       Re: number of Trangles in a graph-network

• To: mathgroup at smc.vnet.net
• Subject: [mg99376] Re: number of Trangles in a graph-network
• From: dh <dh at metrohm.com>
• Date: Mon, 4 May 2009 06:00:51 -0400 (EDT)
• References: <gtefaf\$197\$1@smc.vnet.net>

```
Hi Luca,

try e.g.:

=======================

Needs["Combinatorica`"];

Needs["GraphUtilities`"]

g = RandomGraph[7, 0.5];

ShowGraph[g, VertexNumber -> True]

triangles = {};

Do[   (*loop over first point*)

t = ad[[i, i + 1 ;; -1]];(*take upper half*)

t = i + Position[t, 1] // Flatten;

t = Subsets[t, {2}];(*possible 2. and 3. point*)

t = Select[t,

ad[[Sequence @@ #]] == 1 &];(*check if 2. and 3. point connected*)

t = Prepend[#, i] & /@ t;

triangles = Join[triangles, t];

, {i, 1, Length[ad]}];

triangles

======================

Daniel

Luca Cinacchio wrote:

> Greetings,

>

> having a graph (network, i.e. one created with RandomGraph) wich can have

> not connected nodes, I would like to count the total number of triangles

> inside the graph.

> I gave a look to Combinatorica and its related book by Pemmaraju Skiena,

> but I did'nt find any solution (maybe I am wrong). Do you know if there is

> a easy way to answer this problem with Mathematica and/or Combinatorica?

> Thanks in advance.

>

```

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