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Re: Re: Using GraphPlot to draw an empty graph

• To: mathgroup at smc.vnet.net
• Subject: [mg105435] Re: [mg105381] Re: [mg105358] Using GraphPlot to draw an empty graph
• From: "J. McKenzie Alexander" <jalex at lse.ac.uk>
• Date: Wed, 2 Dec 2009 06:27:52 -0500 (EST)
• References: <200911291011.FAA16287@smc.vnet.net> <200911301111.GAA13302@smc.vnet.net>

Many thanks to all those who responded. One further question: how does one assign labels to edges if calling GraphPlot on an adjacency matrix? I tried the following (which struck me as a natural guess at what the syntax might be), but it failed:

GraphPlot[
{ {0, {1, 0.5}, {1, 0.5}},
{ {1, 0.5}, 0, {1, 0.5}},
{ {1, 0.5}, {1, 0.5}, 0}}, MultiedgeStyle -> True]

>From what I see in the documentation, there doesn't seem to be a way to include edge labels using the adjacency matrix representation, unless I explicitly override EdgeRenderingFunction. Is that right?

Cheers,

Jason


On 30 Nov 2009, at 11:11, Murray Eisenberg wrote:

> You can finesse this by using the form
>
>   GraphPlot[m]
>
> where m is the adjacency matrix.  For example, for a 3-vertex null graph:
>
>   GraphPlot[ConstantArray[0, {3, 3}]]
>
>
> J. McKenzie Alexander wrote:
>> Hello,
>>
>> Is there a way of making GraphPlot draw an empty graph? I realise that
>> this is an ill-defined question if one uses the default options for
>> GraphPlot because there is no way for GraphPlot to know how many
>> vertices it should draw. However, it turns out that even if one set a
>> custom value for VertexCoordinateRule the vertices aren't drawn:
>>
>> GraphPlot[{},
>> VertexRenderingFunction -> ({Black, Disk[#1, 0.05] } &),
>> VertexCoordinateRules ->
>> Table[{Cos[theta], Sin[theta]}, {theta, 0, 2 Pi, 2 Pi/11}]
>> ]
>>
>> I know that I could easily draw this "by hand" using Graphics, but I
>> have good reason for wanting to use GraphPlot. (I wrap the GraphPlot in
>> Dynamic where the list of edges is specified by a variable. Most of the
>> time the variable contains a connected graph, but sometimes it is
>> empty.)
>>
>> As an aside, the following "works" as a way of giving the impression of
>> an empty graph, but it does so by forcing each node to have a self-loop
>> (and then suppressing those edges from being drawn). It would be nice to
>> have a cleaner solution.
>>
>> GraphPlot[Table[i -> i, {i, 0, 11}],
>> VertexRenderingFunction -> ({Black, Disk[#1, 0.05]} &),
>> SelfLoopStyle -> None,
>> VertexCoordinateRules ->
>> Table[N[{Cos[theta], Sin[theta]}], {theta, 0, 2 Pi, 2 Pi/11}]
>> ]
>>
>> Cheers,
>>
>> Jason
>>
>> --
>> Dr J. McKenzie Alexander
>> Department of Philosophy, Logic and Scientific Method
>> London School of Economics and Political Science
>> Houghton Street, London WC2A 2AE
>>
>>
>>
>>
>
> --
> 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
>

--
Dr J. McKenzie Alexander
Department of Philosophy, Logic and Scientific Method
London School of Economics and Political Science
Houghton Street, London WC2A 2AE




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  • Re: Re: Re: Using GraphPlot to draw
    • From: Murray Eisenberg <murray@math.umass.edu>