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Re: [igraph] community detection

From: zhengjun chen
Subject: Re: [igraph] community detection
Date: Wed, 10 Feb 2010 15:48:50 -0500

Thanks. Another question is how the community is indexed? That is, we say some vertices are in community 0, others are community 1. What is the order of community index? In other words, why this cluster is called community 0, and the other is called community 1? 

On Wed, Feb 10, 2010 at 2:19 PM, Tamas Nepusz <address@hidden> wrote:
> Then I use igraph_community_to_membership () to create a membership vector from a community structure dendrogram. My question is how to fill the parameter steps in this function. Right now I use the value corresponding largest modularity.
That's what I would do as well. Actually, that's also exactly what the Python interface does.

> I find that there are several largest modularity values in my case. In other words, several steps have the same modularity. They do not have the same resulting membership. So, which steps I should choose?
Whichever you want ;) I'd choose either the smallest or the largest. Note that if you are working with the fast greedy algorithm, the modularity values that are equal to each other should happen at consecutive numbers of steps due to how the algorithm works. (I.e. it can be shown that once the modularity started to decrease after a merge, it will keep on decreasing until it eventually reaches zero).


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Graduate research assistant
Dept of Computer Science and Engineering
Lehigh University

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