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Gephi Workshop 1

Gephi Workshop 1. David Crowley Maciej Dabrowski. Open Gephi On the lab machines it might have to “install” or “download” it but should only take 2-3 mins We are going to play with the “Les- Miserables.gexf ” sample file to start

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Gephi Workshop 1

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  1. Gephi Workshop 1 David Crowley MaciejDabrowski

  2. Open Gephi • On the lab machines it might have to “install” or “download” it but should only take 2-3 mins • We are going to play with the “Les-Miserables.gexf” sample file to start • Save a copy so you can always start again with the original file

  3. Change to Directed

  4. Les Miserables Network • Co-appearance weighted network of characters in the novel “Les Miserables” from Victor Hugo. • Nodes are placed randomly so it may look different for you

  5. Controls

  6. Layouts • Layout algorithms sets the graph shape, it is the most “essential action” (for visualising) • Graphs are usually layouted with “Force-based” algorithms. Their principle is easy, linked nodes attract each other and non-linked nodes are pushed apart • Layout Panel • Shows layout choice • And Layout Properties

  7. Force Atlas 2 • Run the layout for a few seconds and press stop • You should end up with a graph like this (not exactly the same or it could even be quite different)

  8. Layout Properties • The purpose of Layout Properties is to let you control the algorithm in order to make a aesthetically pleasing representation • Change Scaling (repulsion) to a high number and see what happens and then make it small • Each time we need to run and stop the layout before any visible change happens.

  9. Layout with Scaling @ 50

  10. Ranking • Choose Ranking on the Right Hand Side panel above the layout panel • Nodes should be selected • In the drop down menu you should have three options • Degree • Indegree • Outdegree

  11. Ranking • Choose Degree • Click Apply • Now your graph should be coloured in • You can change the colour settings by clicking on the colour bar

  12. Result List • Click on Result List as highlighted by the red arrow • Click Apply • Now you should see the nodes listed by Rank

  13. Metrics • We will calculate the average path length for the network. • It computes the path length for all possibles pairs of nodes and give information about how nodes are close from each other

  14. Choose Directed – Click OK

  15. Results

  16. Ranking • In the Ranking Panel now in Nodes, we have more metrics • Every (or almost every time) you run a metric you add a new way to rank the graph

  17. Ranking (size) with overlap turned off

  18. Community Detection (Modularity) • Community Detection – used a lot! • Can we predict collapse of online communities? • Concept of hubs – key points in the network • Crime networks – old studies on white collar crime

  19. Modularity • Run modularity • Now you can rank nodes by modularity • This should identify “communities”

  20. Partition • If you click on Partition (next to Ranking) • Press Refresh • You can partition by Modularity Class

  21. Filters • You can run Filters on your graph • Useful for large graphs • Finds components or hides components

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