Re: Convert directed graph to undirected graph

*To*: mathgroup at smc.vnet.net*Subject*: [mg111228] Re: Convert directed graph to undirected graph*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Sat, 24 Jul 2010 05:07:24 -0400 (EDT)

Of course the original graph-like object was a list of rules and not a Combinatorica-type object with head Graph. To get back to the original lit-of-rules object, one can use the following function (I believe this was posted some time ago to MathGroup, but at the moment I forget its author): RuleListFromGraph[Graph[edges_, vertices_, ___]] := Module[{vrules}, vrules = DeleteCases[ Thread[Range[ Length[vertices]] -> (VertexLabel /. vertices[[All, 2 ;;]])], _ -> VertexLabel]; Replace[ Transpose[{Rule @@@ (edges[[All, 1]] /. vrules), EdgeLabel /. edges[[All, 2 ;;]]}], {a_, EdgeLabel} -> a, {1}]] In the example in the post below, one obtains: RuleListFromGraph[gr1u] {1->2,1->3,1->4,2->3,2->4,4->4} Comment: I really wish WRI would at very long last completely rationalize the dichotomy between the newer kernel functions for dealing with lists-of-rules as graphs, on the one hand, and Combinatorica Graph-objects, on the other hand. On 7/23/2010 7:09 AM, juan flores wrote: > Needs["Combinatorica`"]; > Needs["GraphUtilities`"]; > gr1 = > ToCombinatoricaGraph[{1 -> 2, 2 -> 1, 3 -> 1, 3 -> 2, 4 -> 1, 4 -> 2, > 4 -> 4}] > ShowGraph[gr1] > gr1u = MakeUndirected[gr1] > ShowGraph[gr1u] -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305