Re: [igraph] igraph_community_leading_eigenvector_step implementation

[Gábor Csárdi]

Al, as far as I can see both these functions do the same. The
modularity is not explicitly calculated, but according to the original
paper, and also http://arxiv.org/abs/physics/0602124 the leading
eigenvector of the modularity matrix will be negative if the split
would decrease the modularity, and in this case we don't split.

I don't really know what difference you can see between the two
functions, but I coded these quite a while ago, so can't remember all
the details, so I might be wrong.
Where does igraph_community_leading_eigenvector calculate the modularity?

Best,
Gabor

On Sat, Jan 10, 2009 at 6:06 PM, Al <address@hidden> wrote:
> Hi
>
> I am a developer tasked with generalizing the implementation of the M.
> Newman community detection algorithm to accept weighted edges. We want
> to use the step wise variation of the function (located in
> communities.c under the igraph_community_leading_eigenvector_step
> function). On inspection of the source code, it is not obvious to me
> that he modularity calculation is actually being preformed. However,
> in the non-step was variation of the function
> (igraph_community_leading_eigenvector), I notice that it is properly
> implemented. So I am wondering if the step wise variation is properly
> implemented? and if so maybe some insight could be shed on where it is
> preforming the M. Newman modularity calculation.
>
> Thanks
> Al Tucker
>
>
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-- 
Gabor Csardi <address@hidden>     UNIL DGM