Tore Opsahl

Clustering in two-mode networks

September 11, 2009 at 12:00 am Leave a comment

Many network dataset are by definition two-mode networks. Yet, few network measures can be directly applied to them. Therefore, two-mode networks are often projected onto one-mode networks by selecting a node set and linking two nodes if they were connected to common nodes in the two-mode network. This process has a major impact on the level of clustering in the network. If three or more nodes are connected to a common node in the two-mode network, the nodes form a fully-connected clique consisting of one or more triangles in the one-mode projection. Moreover, it produces a number of modeling issues. For example, even a one-mode projection of a random two-mode network with same number of nodes and ties will have a higher clustering coefficient than the randomly expected value. This post represents an attempt to overcome this issue by redefining the clustering coefficient so that it can be calculated directly on the two-mode structure. I illustrate the benefits of such an approach by applying it to two-mode networks from four different domains: event attendance, scientific collaboration, interlocking directorates, and online communication.

Entry filed under: Network thoughts. Tags: actors, affiliation networks, arcs, bipartite networks, clustering coefficient, community, complex networks, degree, edges, embeddedness, global, graphs, Links, local, network, nodes, reinforcement, social network analysis, strength of ties, ties, two-mode networks, undirected networks, valued networks, vertices.