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'Advanced Network Analysis / Pajek: Large ... - Vladimir Batagelj

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V. <strong>Batagelj</strong>: <strong>Analysis</strong> and visulization of large networks with <strong>Pajek</strong> 56<br />

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Generalized cores<br />

The notion of core can be generalized to networks. Let N = (V, E, w)<br />

be a network, where G = (V, E) is a graph and w : E → R is a function<br />

assigning values to edges. A vertex property function on N, or a pfunction<br />

for short, is a function p(v, U), v ∈ V, U ⊆ V with real values.<br />

Let NU (v) = N(v) ∩ U. Besides degrees, here are some examples of<br />

p-functions:<br />

pS(v, U) = �<br />

w(v, u), where w : E → R + 0<br />

u∈NU (v)<br />

pM (v, U) = max w(v, u), where w : E → R<br />

u∈NU (v)<br />

pk(v, U) = number of cycles of length k through vertex v in (U, E|U)<br />

The subgraph H = (C, E|C) induced by the set C ⊆ V is a p-core at level<br />

t ∈ R iff ∀v ∈ C : t ≤ p(v, C) and C is a maximal such set.<br />

Methodenforum der Fakultät für Sozialwissenschaften, Universität Wien, 21-22. 6. 2007 ▲<br />

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