title: Finding community structure in very large networks.
abstract: The discovery and analysis of community structure in networks is a topic of considerable recent interest within the physics community, but most methods proposed so far are unsuitable for very large networks because of their computational cost. Here we present a hierarchical agglomeration algorithm for detecting community structure which is faster than many competing algorithms: its running time on a network with n vertices and m edges is O (md log n) where d is the depth of the dendrogram describing the community structure. Many real-world networks are sparse and hierarchical, with m approximately n and d approximately log n, in which case our algorithm runs in essentially linear time, O (n log(2) n). As an example of the application of this algorithm we use it to analyze a network of items for sale on the web site of a large on-line retailer, items in the network being linked if they are frequently purchased by the same buyer. The network has more than 400 000 vertices and 2 x 10(6) edges. We show that our algorithm can extract meaningful communities from this network, revealing large-scale patterns present in the purchasing habits of customers.
authors.affiliation: Department of Computer Science, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: Aaron
authors.initials: A
authors.lastname: Clauset
authors.forename: M E J
authors.initials: ME
authors.lastname: Newman
authors.forename: Cristopher
authors.initials: C
authors.lastname: Moore