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  Barry Wellman
  _______________________________________________________________________

   S.D. Clark Professor of Sociology, FRSC NetLab Director
   Department of Sociology 725 Spadina Avenue, Room 388
   University of Toronto Toronto Canada M5S 2J4 twitter:barrywellman
   http://www.chass.utoronto.ca/~wellman fax:+1-416-978-3963
   Updating history: http://chass.utoronto.ca/oldnew/cybertimes.php
  _______________________________________________________________________

Role-based similarity in directed networks , arXiv

Abstract: The widespread relevance of increasingly complex networks
requires methods to extract meaningful coarse-grained representations of
such systems. For undirected graphs, standard community detection methods
use criteria largely based on density of connections to provide such
representations. We propose a method for grouping nodes in directed
networks based on the role of the nodes in the network, understood in
terms of patterns of incoming and outgoing flows. The role groupings are
obtained through the clustering of a similarity matrix, formed by the
distances between feature vectors that contain the number of in and out
paths of all lengths for each node. Hence nodes operating in a similar
flow environment are grouped together although they may not themselves be
densely connected. Our method, which includes a scale factor that reveals
robust groupings based on increasingly global structure, provides an
alternative criterion to uncover structure in networks where there is an
implicit flow transfer in the system. We illustrate its application to a
variety of data from ecology, world trade and cellular metabolism.

* [27] Role-based similarity in directed networks, Kathryn Cooper,
Mauricio Barahona, 2010/12/13, arXiv:1012.2726
[27] http://arXiv.org/abs/1012.2726

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