Re: Using GraphPlot to draw an empty graph

*To*: mathgroup at smc.vnet.net*Subject*: [mg105381] Re: [mg105358] Using GraphPlot to draw an empty graph*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Mon, 30 Nov 2009 06:11:42 -0500 (EST)*Organization*: Mathematics & Statistics, Univ. of Mass./Amherst*References*: <200911291011.FAA16287@smc.vnet.net>*Reply-to*: murray at math.umass.edu

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

**References**:**Using GraphPlot to draw an empty graph***From:*"J. McKenzie Alexander" <jalex@lse.ac.uk>