Community Detection with Networkx
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Clustering Methods and Community Detection with NetworkX. A slide deck for the NTU Complexity Science Winter School. For the accompanying iPython Notebook, visit: http://github.com/eflegara/NetStruc
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Community Detection with Networkx
- 2. Walkthrough • Network structure and function • Communities • Community detection algorithms • Divisive • Agglomeratxive • Application: Community detection in framing analysis • Hands-on http://tiny.cc/commdet2017 http://tinyurl.com/commdet2017
- 3. Network Structure • Path length • Diameter • Clustering coefficient • Degree distribution • Centrality measures Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science What would the behaviour of networked systems be based on their structural properties? Structure Func*on
- 4. Communities • Cluster, module, group • A group of nodes that have a higher likelihood of connecting to each other than to nodes from other communities Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science
- 5. Example of Communities • Network: World Wide Web • Communities: Sites on related topics • Network: Friendship network • Communities: Group formation among people • Network: Metabolic networks • Communities: Functional modules • Network: Collaboration network • Communities: Research fields Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science
- 6. Social Networks: Politics, Ideologies Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science The political blogosphere and the 2004 U.S. election: divided they blog by Lada Adamic, Natalie Glance Social media, political change and the #RapplerDebate by Maria A. Ressa and Russell Shepherd
- 7. How does one find the Communities? Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science
- 10. Modularity • Measure the quality of a partition “the fraction of edges that fall within communities, minus the expected value of the same quantity if edges fall at random without regard for the community structure” Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science Mc = ncX c=1 " Lc L ✓ kc 2L ◆2 #
- 11. Modularity Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science Mc = ncX c=1 " Lc L ✓ kc 2L ◆2 # Number of communities Total number of links in Community c Total node degrees in Community c Total number of links
- 12. Modularity Community Structures | EF Legara | 2017 NTU Winter School on Complexity Science Mc = ncX c=1 " Lc L ✓ kc 2L ◆2 # Number of communities Total number of links in Community c Total node degrees in Community c Total number of links 1 2 3 Community 1: " 6 20 ✓ 14 40 ◆2 # " 4 20 ✓ 10 40 ◆2 # Community 3: Mc = 0.50 Community 2: " 7 20 ✓ 16 40 ◆2 #
- 13. Modularity Community Structures | EF Legara | 2017 NTU Winter School on Complexity Science Mc = ncX c=1 " Lc L ✓ kc 2L ◆2 # Number of communities Total number of links in Community c Total node degrees in Community c Total number of links 1 2 3 Mc = 0.35 Community 1: " 4 20 ✓ 10 40 ◆2 # Community 3: " 2 20 ✓ 8 40 ◆2 # Community 2: " 9 20 ✓ 22 40 ◆2 #
- 14. Modularity Community Structures | EF Legara | 2017 NTU Winter School on Complexity Science Mc = ncX c=1 " Lc L ✓ kc 2L ◆2 # Number of communities Total number of links in Community c Total node degrees in Community c Total number of links M = 0
- 15. 1 2 3 Mc = 0.50 M = 0 1 2 3 Mc = 0.35 Optimal Partition Suboptimal Partition One Community Modularity Mc = ncX c=1 " Lc L ✓ kc 2L ◆2 # Community Structures | EF Legara | 2017 NTU Winter School on Complexity Science
- 16. Quantifying Community Structures Divisive • Girvan-Newman Algorithm (edge betweenness) Agglomerative • Hierarchical clustering (distance matrix) • Louvain Method (modularity-maximization) Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science Cut 3 classes Cut 4 classes Cut 6 classes
- 17. Community Detection in Framing Analysis Framing - the “central organizing idea for making sense of an issue or conflict and suggesting what is at stake” Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science EF Legara, C Monterola, C David, and JM Atun, "News Framing of Population and Family Planning Issues via Syntactic Network Analysis", Intl J of Mod Phys C 21, Issue: 1, pp. 51-65 (2010). A Network of Words
- 18. “Frames have been shown experimentally to cause differences in attributions of responsibility among readers or audiences.” Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science
- 19. • 346 news articles (randomly sampled) • Population, family planning, reproductive health, and contraception published between 1987 and 2007 Framing in the News Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science
- 20. Every article assigned to a single dominant frame q Population and Development q Family Planning as Conflict between Government and Church q Women’s and Reproductive Health q Population Management Threatens Morals and Values q Population Growth and Demographic Trends q Others Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science
- 21. Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science Collected Articles Delete stop words and replace with placeholder “xxx” Generalize conceptually similar terms Obtain high-frequency words A Network of Words
- 22. Community Structures | EF Legara | 2016 NTU Winter School on Complexity Science Map words: add edge weight (1u) between nodes if words co- exist in a scanning window Create co-occurrence network Perform cluster analysis