Re: [igraph] Question about community detection

[Gábor Csárdi]

Hi,

On Sat, Dec 19, 2009 at 11:13 PM, zhengjun chen <address@hidden> wrote:
> Hi,
> I have a question about community detection in
> Igraph."igraph_community_leading_eigenvector()" function is used to detect
> communities.
> My question is what is the meaning of "steps" in this function. Does it mean
> the number of community split operation?

yes, the number of attempted split operations.

> When I change this value from 10 to 100, more and more communities have been
> detected. So, the parameter "steps" should be set to what?

Whatever you wish. If you want to make as many steps as possible, then
set it to the number of vertices. (As suggested in the documentation.)

> In addition, I have no idea about how many communities actually exist. So,
> what can I do to verify that the communities detected is good enough?

You can check the modularity score of the communities. If I remember
well, this method stops splitting the communities if the modularity
values cannot be increased by any split.

> I am also a bit confused of the structure igraph_arpack_options_t. Now I
> just initialize it to default values.

Which is fine, as long as the function works. You only need to change
it if you have special graphs, e.g. very sparse ones with long cycles.

Gabor

> --
> Thanks
> zhengjun
>
> Graduate research assistant
> Dept of Computer Science and Engineering
> Lehigh University
>
> _______________________________________________
> igraph-help mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/igraph-help
>
>



-- 
Gabor Csardi <address@hidden>     UNIL DGM