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Is there a way to convert a Delaunay triangulation into a Graph structure, so that one can generate an adjacency matrix of the triangulation?

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    $\begingroup$ You don't need to go through a graph. Once you have the Delaunay triangulation as a set of point-index pairs, you can SparseArray@Thread[pairs -> 1] assuming the indices start from 1. $\endgroup$
    – Szabolcs
    May 23, 2014 at 19:42
  • $\begingroup$ Bigger question: in what format do you have the Delaunay triangulation? $\endgroup$
    – Szabolcs
    May 23, 2014 at 19:43
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    $\begingroup$ BTW you will soon be able to simply DelaunayMesh[pts]["AdjacencyMatrix"]. $\endgroup$
    – Szabolcs
    May 23, 2014 at 19:45
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    $\begingroup$ @Szabolcs soon for what values of soon? $\endgroup$
    – Yves Klett
    May 23, 2014 at 20:56
  • $\begingroup$ @Yves I don't know more than you. $\endgroup$
    – Szabolcs
    May 23, 2014 at 21:35

2 Answers 2

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In version 10, which is at the moment publicly accessible through the Programming Cloud, you can simply use:

DelaunayMesh[points]["AdjacencyMatrix"]

to obtain an adjacency matrix.


The IGraph/M package has support for converting meshes into matrices. This problem would be solved by

mesh = DelaunayMesh[points]
IGMeshCellAdjacencyMatrix[mesh, 0]

0 means the adjacency relation of 0-dimensional mesh cells, i.e. points.

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Since you want to go from DelaunayTriangulation to Graph to AdjacencyMatrix, how about the following (works in version 9.0.1)

pts = RandomReal[4, {25, 2}];

Load the undocumented Region context

Graphics`Region`RegionInit[];

Then,

mesh = DelaunayMesh[pts];

graph = Graph @ MeshTopologyGraph[mesh][[1]];

( matrix = AdjacencyMatrix[graph] ) // MatrixForm

Mathematica graphics

OR

pairs = MeshTopologyGraph[mesh][[1]] /. Rule -> List

matrix = Normal @ SparseArray[Thread[pairs -> 1]]

Surprise , surprise as suggested by Szabolcs (only, you can do it now in v9) but with a little twist, you can get it directly:

matrix = mesh[[1]]["AdjacencyMatrix"]
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  • $\begingroup$ It doesn't work for me on v8.. Picture here. $\endgroup$
    – Öskå
    May 23, 2014 at 23:05
  • $\begingroup$ @Öskå. Hmmm. I don't have v8, but good to know. It works fine in v9.0.1 $\endgroup$
    – RunnyKine
    May 23, 2014 at 23:15
  • $\begingroup$ @Öskå, does the Region context work for you in v8? $\endgroup$
    – RunnyKine
    May 23, 2014 at 23:17
  • $\begingroup$ DelaunayMesh doesn't seem to work. here. Could you please set a SeedRandom and upload a picture of the Graph in the comments? :) $\endgroup$
    – Öskå
    May 23, 2014 at 23:19
  • $\begingroup$ @Öskå here. SeedRandom[2345] $\endgroup$
    – RunnyKine
    May 24, 2014 at 0:03

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