# Tagged Questions

Questions about handling graphs in Mathematica, graph theory, graph visualization, GraphPlot, the built-in Graph type and the Combinatorica package.

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### How to convert an image to a graph and get the positions of the edges?

I am trying to convert an image to a graph. My image is already skeletonized and looks pretty much like this: What I need to do is identify all vertices and edges, and in particular get a list of ...
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### Finding a “not-shortest” path between two vertices

In designing a routine for making a simple three dimensional (5x5x5) labyrinth, I realized that my solutions (a solution is a labyrinth includes a single path from {1, 1, 1} to {5, 5, 5} in a 5 x5x5 ...
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### How can I speed up the classic GA for graph coloring?

I'm trying to compute the chromatic number of this graph (which is 28): g = Import@"http://www.info.univ-angers.fr/pub/porumbel/graphs/dsjc250.5.col"; My genetic ...
522 views

### Import and Plot Git Commit History

What might be the easiest to import and plot all commit history for a github project? I'm looking for something similar to the following.
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### A question about weighted graphs

Bug introduced in 8.0 or earlier and persisting through 10.3 I need create a weighted graph with given data. Number of nodes: $53$ $\quad$ Number of edges: $91$ ...
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### Drawing a graph with specified edge lengths

I was wondering if it was possible to ask Mathematica to draw a graph provided some set of vertices: $(v_1, ..., v_N) \in V$ connected by $M$ edges $(e_1, ..., e_M) \in E$, where the length of each ...
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### How to plot layered graphs?

Given a directed acyclic graph, there is always a possibility to plot the graph as layers, where nodes always send edges into one direction (usually down), to successive layers, and never backwards. ...
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### Travelling salesman with start and end points for 30 points

I am doing a route optimisation for delivery vehicles and failing dismally. Please see problem statement below. My current solution uses FindShortestTour, but this does not have defined start and end ...
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### Nested list to graph

The following nested list can be regarded as a representation of a (tree) graph: ...
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### IsomorphicGraphQ fails to recognize that two empty graphs are identical

Bug introduced in 9.0.1 or earlier and persisting through 10.4.0 Consider the following two graphs: ...
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### Is it possible to export a graph as graphic to Excel?

It is straightforward to export lists to Excel with Export. Can I export a graphic image, too? This does not work: ...
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### Is there something akin to “SubgraphIsomorphismQ” in Mathematica 9?

Provided two unlabeled graphs, $G$ and $H$, I would like to test where $H$ is a subgraph of $G$. In other words, I'd like to test whether we can prune some fixed number of vertices or edges from $G$ ...
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### Finding all minimal paths in site percolation?

I want to find all minimal site percolation paths from the left side to the right side, small demo grid. A related question is here on finding bond percolation paths instead of minimal site ...
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### Combinatorica: Girth[] and FindCycle[] disagreement

Warning: run the following code in a fresh Mma session, as some symbols could be shadowed (depending on your Mma version) While trying to answer this question, I fell into the following: ...
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### Using Gather to rearrange my data

I have a list of elements: {{1, 2}, {1, 5}, {2, 6}, {3, 7}, {4, 8}, {5, 6}, {5, 9}, {9, 13}, {10,11}, {11, 12}, {11, 15}, {15, 16}} I have to divide it into ...
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### How can I display a multigraph with different colored edges?

I'm new to Mathematica(version 9) and I'm trying to display a multigraph with different colored edges. Here's my code so far: ...
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### Keeping vertexcoordinates after adding a new vertex

I want to add a new vertex to a graph, with fixed VertexCoordinates but when I use VertexAdd, the new graph does not have the VertexCoordinates of the previous one. ...
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### Is it possible to generate a Hasse Diagram for a defined relation?

I'm looking for a way to create a Hasse Diagram from a given partial order binary relation. The relation will be given explicitly, for example: ...
263 views

### Graph does not evaluate some options when not displayed

How can I force Graph to evaluate all its options without actually displaying the graph itself? Evaluating the following code ignores the ...
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### DeleteVertex in Kpartite graph

How can i make K7,2 graph and how can i delete 2 vertex? Btw, i need to use package -> Combinatorica; I tried this: ...
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### EdgeRenderingFunction question

Bug introduced in 9.0 and fixed in 10.0.0 (Edit 1 : I added this paragraph after the original post, for context) Some context for this question can be found in another post (http://mathematica....
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### Adding an image background to a graph that uses vertexposition

Hello Mathematica stackexchange community! I need your help on a research project. I'm looking to create a graph g with vertices in specifies places and then use an image I have as the background of ...
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### Incompability between v5-6 and v10 with Graphs and Oriented Graphs pkgs?

Notice that "although the v6 Packages are available at the link in the answer above they are not fully compatible with v10". The errors 1, 2 and 3 in Mathematica 10 student edition may be due to ...
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### How can you delete a list of vertices from a GridGraph?

Given a grid graph: and delete the vertices {3, 4, 5, 11, 14, 15, 16, 17, 18, 19, 21, 23, 26, 27, 30} and preserve the structure. There is the ...
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### Caching of Graph Graphics

In this answer, Simon Woods concludes that when you display an expression with head graph more than once, something is getting stored somewhere. I looked into it too and found out this only happens if ...
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### Finding All Chordless Simple Cycles In A Graph

I am doing a research on networks which consists of polygons with different number of sides. I am trying to find all simple cycles in a network which are chordless. As an example, consider the ...
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### How to count all cliques (not just maximal ones) in graphs?

How can I count the numbers of $r$-cliques in a graph? In other words, the number of triangles, the number of $K_4$, the number of $K_5$ etc. I have tried for example ...
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### BezierCurve in EdgeShapeFunction fails when used on multiedges graph

I would like to create a network graph with curved edges. To do this, I wrote this function: ...
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### Why don't the arrowheads show for this directed graph?

Bug introduced in version 9.0 or earlier and fixed in 10.3 It's very weird, but the first graph is shown as undirected (dots connected by lines, not arrows. The second is shown as directed, with ...
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### Deleting isomorphic graphs efficiently

I'm trying to delete isomorphic graphs from a large list. My solution is as follows: DeleteIsoG1[gl_List]:= Module[{}, DeleteDuplicates[gl,IsomorphicGraphQ]]; ...
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### How does Mathematica calculate its AdjacencyMatrix[ ] and VertexDegree[ ]

I define a graph: ...
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### Separating disconnected graph objects without losing vertex coordinate assignments

Say I have a graph Gtest, which has multiple disconnected components. I found that I can isolate individual components while retaining vertex coordinate ...
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### How to implement the directed Barabasi-Albert algorithm in Mathematica?

Does anyone know how to implement an efficient version of the [directed Barabasi-Albert algorithm][1] in Mathematica that scales until hundred of thousands nodes? The directed network mechanism is ...
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### Deleting Vertices in GridGraph

Take a simple GridGraph: g = GridGraph[{3, 3}, VertexLabels -> "Name", ImageSize -> 150, ImagePadding -> 10] I am ...
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### How can I change the Graph required data such as EdgeWeight,VertexWeight,EdgeCapacity,VertexCapacity in the Graph?

I asked this question in different form and because I couldn't receive the proper answer so I have to change my question.I know that was my fault sorry.I need to change the Matrix Data of nodes and ...
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### Citation of the algorithms used in FindGraphCommunities

For my research work I need to put a comparison of different community detection algorithms. Instead of implementing all those algorithms once again, I would like to use the methods already provided ...
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### Graph adjacency matrix with unconnected nodes

I am trying to display a series of 9x9 adjacency matrices which represent directed graphs on a 3x3 grid. The issue I am running up against is this (compounded by that fact that I don't really know how ...
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My graph is ...
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### References on functions FindGraphPartition and FindGraphCommunties

Does somebody have some interesting references on the FindGraphPartition and FindGraphCommunties[.., Method -> "Spectral"] ...
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### What exactly does LocalClusteringCoefficient compute for directed graphs?

For undirected graphs, the LocalClusteringCoefficient of vertex v is ...
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### Graphs' options vs JournalArticle stylesheet

Bug introduced in 10.4 and persists through 10.4.1 [...] This GridGraph behavior does appear to be a regression in Mathematica 10.4 from earlier versions. As ...
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### VertexRenderingFunction (or EdgeRenderingFunction) with movable nodes?

In GraphPlot, I'd like to use VertexRenderingFunction (VRF) and have the resulting object behave the same way under dragging verticies as it does when I do not use VRF. The same issue occurs for ...
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### Intelligent vertex placement in large tree graphs

This question about graph layout is fairly general, but can be illustrated in the case of the Collatz Conjecture. Collatz created the following function over integers greater than 1: If the integer ...
404 views

### How to convert a sparse array to a graph?

s = Import["hello.mat"]; t = GraphEmbedding[Graph[s[[1]]], "GridEmbedding"]; I get the following error: GraphEmbedding::graph: A graph object is expected ...
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### How to generate a random tree?

Is it possible to generate a random tree without explicitly constructing a random adjacency matrix that satisfies tree properties? How about a random directed tree? Edit: incredible answer by ...
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### Is there a way to convert an image into a Graph?

I'm trying to convert an image with several overlapping dots into a Graph. The goal is to be able to derive the Kirchhoff matrix for the randomly created "network ...
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### Reconstruct a graph from an image (curved edges and edge crossings)

Actually, I posted a very similar question before this.How to generate a Graph from a picture of a graph Dr. belisarius's answer have answered that question, but I find a limitation in that method: ...
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### Longest path in 0/1 matrix

I have a matrix of 0's and 1's forming a number of disjoint paths:   I would like to find the lengths of the paths, and from that "spectrum," the longest length (in the above example: 27, ...