Affinity or Resistance Distance between Actors
The notion of resistance distance for a network of actors has been used to measure the closeness (or affinity) between two actors. A generic graph representation of the network of actors lacks the notion of degree of closeness. For example, it does not illuminate whether two actors have acted in one or 10 movies together. However, the plot here highlights how close the actors are, based on the number of movies in which they have collaborated. This refines the idea of Erdős number not only to see the links between actors but how strong they are. The affinity of an actor for himself is defined to be zero.
 Wikipedia. "Collaboration Graph." (Aug 10, 2013) en.wikipedia.org/wiki/Collaboration_graph.
 A. T. Balaban and D. J. Klein, "Co-Authorship, Rational Erdős Numbers, and Resistance Distances in Graphs," Scientometrics, 55(1), 2002 pp. 59–70.