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] ad = AdjacencyMatrix[g] // Normal; 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. >