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## [igraph] community detection

 From: zhengjun chen Subject: [igraph] community detection Date: Wed, 27 Jan 2010 22:17:55 -0500

Hi,

I use "fastgreedy" community detection algorithm to find community in my graph.
It detects two communities 1 and 2. Each community consists of some high-degree vertices.
To some extent, the vertex's degree reflects the role of the vertex in its community.
I look at these high-degree vertices, and meet a problem.
One vertex called A belongs to community 2. It has connections to two high-degree vertices B and C of community 2. But it also has connections to two high-degree vertices D and E of community 1.
So, why vertex A is divided into community 2? I look at its neighbors.
It has about 30 common neighbors with vertices D and E, while only has 10 common neighbors with B and C.
It goes against my intuition that is vertices in the same community should share more neighbors.
So, I am wondering whether I get a wrong result of community division. Or any other explanation for my problem.

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Thanks
zhengjun