关于聚类系数的原汁原味的介绍,可以参考小世界网络这篇论文 [1]:
The clustering coefficient C(p) is defined as follows. Suppose that a vertex v has kv neighbours; then at most kvðkv 21Þ=2 edges can exist between them (this occurs when every neighbourof v is connected to everyother neighbour of v). Let Cv denote the fraction of these allowable edges that actually exist.
Define C as the average of Cv over all v. For friendship networks, these statistics have intuitive meanings: L is the average number of friendships in the shortest chain connecting two people;
Cv reflects the extent to which friends of v are also friends of each other; and thus C measures the cliquishness of a typical
friendship circle. The data shown in the figure are averages over 20 random realizations of the rewiring process described in Fig.1, and have been normalized by the values L(0), C(0) for a regular lattice. All the graphs have n ¼ 1;000 vertices and an average degree of k ¼ 10 edges per vertex. We note that a logarithmic horizontal scale has been used to resolve the rapid drop in L(p), corresponding to the onset of the small-world phenomenon.
During this drop, C(p) remains almost constant at its value for the regular lattice, indicating that the transition to a small
world is almost undetectable at the local level .
用白话解释一下:</