Null model: Difference between revisions

Revision as of 14:41, 31 January 2016

Revision as of 20:36, 31 January 2016

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{{for|use in ecology|Theoretical ecology}}

In mathematics, in the study of statistical properties of [[Graph (discrete mathematics)|graphs]]{{dn|date=January 2016}}, the '''null model''' is a graph which matches one specific graph in some of its structural features, but which is otherwise taken to be an instance of a [[random graph]]. The null model is used as a term of comparison, to verify whether the graph in question displays some feature, such as community structure, or not.

One null model is that proposed by Newman and Girvan and consists of a randomized version of the original graph, where edges are rewired at random, under the constraint that the expected degree of each vertex matches the degree of the vertex in the original graph.<ref>{{cite journal|last=M.E.J|first=Newman|author2=M.Girvan |title=Finding and evaluating community structure in networks|journal=Phys. Rev. E|year=2004|volume=69|issue=2|doi=10.1103/physreve.69.026113 }}</ref>