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Re: changing style of vertices for ShowGraph with Combinatorica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg86332] Re: [mg86270] changing style of vertices for ShowGraph with Combinatorica
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Sat, 8 Mar 2008 05:44:58 -0500 (EST)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200803070729.CAA19892@smc.vnet.net> <C63D1D41-0058-431D-A84D-4418E66DBF46@lse.ac.uk>
  • Reply-to: murray at math.umass.edu

Yes, GraphPlot seems to permit making nice vertices (or edges), but then 
the labeling -- either with a Graph object from Combinatorica or just 
the kind of graph described by the GraphPlot reference page -- does not 
seem to admit vertex labels or edge labels, at least so far as I can 
see.  For example, neither of the following displays either vertex 
labels or edge labels:


GraphPlot[Cycle[3], Method -> Automatic, VertexLabeling -> True,
  EdgeLabeling -> True, EdgeRenderingFunction -> ({Black, Line[#1]} &),
   VertexRenderingFunction -> ({EdgeForm[{Thickness[0.005], Red}],
      Yellow, Disk[#1, 0.04]} &)]

GraphPlot[{{v1 -> v2, "a"}, {v2 -> v3, "b"}, {v3 -> v1, "c"}},
  Method -> Automatic, VertexLabeling -> True, EdgeLabeling -> True,
  EdgeRenderingFunction -> ({Black, Line[#1]} &),
  VertexRenderingFunction -> ({EdgeForm[{Thickness[0.005], Red}],
      Yellow, Disk[#1, 0.04]} &)]

On the other hand, if I remove he VertexRenderingFunction option, I do 
see vertex labels on the default (yellow boxes) vertex shapes:

  GraphPlot[{v1 -> v2, "a"}, {v2 -> v3, "b"}, {v3 -> v1, "c"}},
   Method -> Automatic, VertexLabeling -> True,
    EdgeLabeling -> True, EdgeRenderingFunction -> ({Black, Line[#1]} &)]

GraphPlot[Cycle[3], Method -> Automatic, VertexLabeling -> True,
  EdgeLabeling -> True, EdgeRenderingFunction -> ({Black, Line[#1]} &)]

Of course this now defeats the purpose of using GraphPlot so as to get 
exactly the kind of vertex shapes that VertexRenderingFunction, above, 
provides.

Similarly with EdgeRenderingFunction.

The kernel function GraphPlot doesn't seem to mesh very well with 
Combinatorica's graph functions.  This all still seems only "half-baked".


J. McKenzie Alexander wrote:
> Take a look at GraphPlot, the graph rendering function that is built 
> into the Mathematica kernel.  I switched from using ShowGraph to 
> GraphPlot after realising that it was (a) faster and (b) easier to 
> customise.  Here's what you want:
> 
> GraphPlot[
>  Cycle[3],
>  Method -> None,
>  EdgeRenderingFunction -> ({Black, Line[#1]} &),
>  VertexRenderingFunction -> ({EdgeForm[{Thickness[0.005], Red}], Yellow,
>      Disk[#1, 0.04]} &)
>  ]
> 
> You need to specify Method->None, otherwise GraphPlot will override the 
> specified positions of the vertices in the graph and use its own default 
> vertex positioning algorithm.
> 
> VertexRenderingFunction is what you need to define in order to customise 
> the appearance of the vertices.
> 
> I provided a definition of EdgeRenderingFunction just so that the edges 
> are rendered in the same way as ShowGraph.
> 
> Cheers,
> 
> Jason
> 
> -- 
> J. McKenzie Alexander
> Department of Philosophy, Logic and Scientific Method
> London School of Economics and Political Science
> Houghton Street, London WC2A 2AE
> 
> 
> On 7 Mar 2008, at 07:29, Murray Eisenberg wrote:
> 
>> With Mathematica 6, I can change the default style (medium black disk)
>> for rendering the vertices of a Combinatorica Graph like this:
>>
>>   Needs["Combinatorica`"]
>>
>>   g = Cycle[3];
>>   ShowGraph[g, VertexStyle -> Disk[Large], VertexColor -> Red]
>>
>> But how can I, for example, change the vertex style so it is, say, a
>> large yellow disk with a thick red boundary?  Or even just change it to
>> be a circle?  I tried "obvious" things like the following, but they
>> cause errors:
>>
>>   ShowGraph[g, VertexStyle -> Graphics[Circle[], ImageSize -> 20]]
>>
>> -- 
>> 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
>>
> 
> 
> 
> 
> 
> 
> Please access the attached hyperlink for an important electronic 
> communications disclaimer: 
> http://www.lse.ac.uk/collections/secretariat/legal/disclaimer.htm
> 

-- 
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


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