Re: [igraph] Comparing large graphs

[Charles Novaes de Santana]

Wow!! Thank you very much, Tamás! It is a lot of valuable
information!!! I guess I have a lot to study this weekend! :)

By the way, I was "translating" some Igraph-R-code to Igraph-C-code in
order to use the advantages of C in working with larger matrices.

But using this version of Igraph for C (version 0.6) I was wondering
some points:

First, I was wondering if Igraph considers IGRAPH_INFINITY as zero or
as other value. I am working with shortest-paths matrices and I would
like the distance between two vertices that can not reach each other
to be zero.

Besides of that, I am using some igraph-functions to manipulate
matrices (they are very good, thank you for sharing it!!). I thought
about using the function "igraph_matrix_scale" to divide a matrix by a
scalar value just by using a number between 0 and 1 as the "by"
parameter. But I realized that the function only accepts integer
values (I tryied to do "igraph_matrix_scale(matrix,1./2)" and it gave
me a zero-matrix). I would like to "divide" the shortest path matrix
by the diameter of the network. Is there any way to do it?

Sorry for the inconvenience, and thank you again for all your valuable help!

Best,

Charles


On Tue, Dec 4, 2012 at 8:27 PM, Tamás Nepusz <address@hidden> wrote:
>> If I remember right, some months ago somebody posted here about
>> measures to compare networks. I looked for this post in the historial
>> of the list, but I didn't find it, sorry.
> This is a thread that seems related, although it is quite old:
>
> http://lists.gnu.org/archive/html/igraph-help/2008-04/msg00009.html
>
> However, the conclusion is still the same: there is no built-in network 
> comparison measure in igraph right now. Besides the options mentioned in that 
> particular thread, another possibility is to calculate the top few 
> eigenvalues and eigenvectors of the adjacency matrix of the graph, and then 
> compare these values and vectors. Others have studied this in much greater 
> detail than me so I'd recommend to Google for "spectral graph comparison" if 
> you are interested. This paper could be a good starting point:
>
> http://www.comp.leeds.ac.uk/bmvc2008/proceedings/2005/papers/162/bmvc2005b.pdf
>
> You can also compare the motif profiles of the graphs:
>
> http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0015765
>
> Yet another option that comes to my mind is to use some technique that 
> compresses the graph into a much smaller matrix while preserving the most 
> important structural features and then compare the matrices:
>
> http://arxiv.org/abs/cond-mat/0703470
>
> Best,
> T.
>
>
>
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-- 
Um axé! :)

--
Charles Novaes de Santana
http://www.imedea.uib-csic.es/~charles
PhD student - Global Change
Laboratorio Internacional de Cambio Global
Department of Global Change Research
Instituto Mediterráneo de Estudios Avanzados(CSIC/UIB)
Calle Miquel Marques 21, 07190
Esporles - Islas Baleares - España

Office phone - +34 971 610 896
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