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SCAN: A Structural Clustering Algorithm for Networks. Xiaowei Xu ( 徐晓伟 ). Joint Work with Nurcan Yuruk (UALR) and Thomas A. J. Schweiger (Acxiom). Network Clustering Problem.
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SCAN: A Structural Clustering Algorithm for Networks Xiaowei Xu (徐晓伟) Joint Work with NurcanYuruk (UALR) and Thomas A. J. Schweiger (Acxiom)
Network Clustering Problem Networks made up of the mutual relationships of data elements usually have an underlying structure. Because relationships are complex, it is difficult to discover these structures. How can the structure be made clear? Stated another way, given simply information of who associates with whom, could one identify clusters of individuals with common interests or special relationships (families, cliques, terrorist cells).
An Example of Networks • How many clusters? • What size should they be? • What is the best partitioning? • Should some points be segregated?
A Social Network Model Individuals in a tight social group, or clique, know many of the same people, regardless of the size of the group. Individuals who are hubs know many people in different groups but belong to no single group. Politicians, for example bridge multiple groups. Individuals who are outliers reside at the margins of society. Hermits, for example, know few people and belong to no group.
The Neighborhood of a Vertex Define () as the immediate neighborhood of a vertex (i.e. the set of people that an individual knows ).
Structure Similarity The desired features tend to be captured by a measure we call Structural Similarity Structural similarity is large for members of a clique and small for hubs and outliers.
Structural Connectivity [1] -Neighborhood: Core: Direct structure reachable: Structure reachable: transitive closure of direct structure reachability Structure connected: [1] M. Ester, H. P. Kriegel, J. Sander, & X. Xu (KDD'97)
Structure-Connected Clusters hub outlier • Structure-connected cluster C • Connectivity: • Maximality: • Hubs: • Not belong to any cluster • Bridge to many clusters • Outliers: • Not belong to any cluster • Connect to less clusters
2 3 5 1 4 7 6 0 11 8 12 10 9 13 Algorithm = 2 = 0.7
Algorithm 2 3 = 2 = 0.7 5 1 4 7 6 0 11 8 12 10 9 0.63 13
Algorithm 2 3 = 2 = 0.7 5 1 4 7 6 0 0.67 11 8 0.82 12 10 0.75 9 13
2 3 5 1 4 7 6 0 11 8 12 10 9 13 Algorithm = 2 = 0.7
Algorithm 2 3 = 2 = 0.7 5 1 4 7 6 0 11 8 12 10 9 0.67 13
Algorithm 2 3 = 2 = 0.7 5 1 4 7 6 0 11 0.73 8 0.73 12 0.73 10 9 13
Algorithm 2 3 = 2 = 0.7 5 1 4 7 6 0 11 8 12 10 9 13
Algorithm 2 3 = 2 = 0.7 5 1 4 7 0.51 6 0 11 8 12 10 9 13
Algorithm 2 3 = 2 = 0.7 5 1 4 7 6 0 0.68 11 8 12 10 9 13
Algorithm 2 3 = 2 = 0.7 5 1 4 7 6 0 11 8 12 0.51 10 9 13
Algorithm 2 3 = 2 = 0.7 5 1 4 7 6 0 11 8 12 10 9 13
Algorithm 2 3 = 2 = 0.7 5 1 0.51 4 7 0.68 6 0 0.51 11 8 12 10 9 13
Algorithm 2 3 = 2 = 0.7 5 1 4 7 6 0 11 8 12 10 9 13
Running Time [2] A. Clauset, M. E. J. Newman, & C. Moore, Phys. Rev. E70, 066111 (2004). Running time = O(|E|) For sparse networks = O(|V|)
Are you ready for some football? Given only the 2006 schedule of what schools each NCAA Division 1A team met on a football field, what underlying structures could one discover?
789 Contests • 119 Division 1A school who play: • schools in their conference • schools in other 1A conferences • independent 1A schools (e.g. Army) • schools in sub-1A conferences (e.g. Maine)
USC Pacific 10 Utah State Western Athletic Vanderbilt SEC Alabama SEC Auburn SEC Southeast Missouri State Non 1A Mississippi SEC Louisiana Monroe Sun Belt SouthCarolina SEC Tennessee SEC Mississippi State SEC LSU SEC Florida SEC Wisconsin Big 10 Consider Arkansas’ Schedule:
Result of FastModularity Alg. [2]: [2] A. Clauset, M. E. J. Newman, & C. Moore, Phys. Rev. E70, 066111 (2004).
Conclusion • We propose a novel network clustering algorithm: • It is fast O(|E|), for scale free networks: O(|V|) • It can find clusters, as well as hubs and outliers • For more information: • See you in poster session this evening at poster board #4 • Email: xwxu@ualr.edu • URL: http://ifsc.ualr.edu/xwxu • Thank you!