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What you have explained here is the Jaccard index (http://en.wikipedia.org/wiki/Jaccard_index), which is very closely related to the cosine similarity measure (http://en.wikipedia.org/wiki/Cosine_similarity). Both measures are used for measuring how similar two samples (sets, clusters, etc) are.
Ph.D. Student, UMN
***** To join INSNA, visit http://www.insna.org ***** A few months ago I stumbled across a simple measure of cluster overlap. Assume two clusters, A and B, that contain a total of n nodes of which m nodes belong to both clusters or, in other words, n is the number of nodes in the union of A and B and m the number of nodes in the intersection of A and B. The measure is something along the lines of overlap=m/n=nodes in intersection/nodes in union. My problem is (1) that I have forgotten where I found this measure and (2) am not 100% sure that it was as simple as I recall. If you recognize this problem, can point me to a source or provide me with a correct or better formula, your help will be much appreciated.John_____________________________________________________________________ SOCNET is a service of INSNA, the professional association for social network researchers (http://www.insna.org). To unsubscribe, send an email message to [log in to unmask] containing the line UNSUBSCRIBE SOCNET in the body of the message.
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