El 07/11/13 13:14, Tiago Peixoto [via Main discussion list for the
graph-tool project] escribió:
> On 11/07/2013 08:01 AM, xenil wrote:
> > Two questions:
> > - The usual katz calculation definition uses the transpose adjacency
> matrix, Is this transposition done in your code?
>
> There are different conventions for the adjacency matrix of directed
> graphs. The code in the library follows the in-neighbours of the
> edge. So the matrix multiplication is performed:
>
> y_i = alpha \sum_j A_ij x_j + beta_i
>
> where A_ij is one if there is an edge in the direction j->i. If you want
> to transpose the matrix, it is easy: You just reverse the direction of
> the graph with g.set_reversed(True).
>
Ok
> > - Is the adjacency matrix normalized when no edge weight is used?
>
> No.
>
I think that for unweighted katz centrality calculation, using the
adjoint matrix, the normalization could be necesary to guarantee
convergence.
There is another normalization on the _init.py file before the C++ BGL
function call, line 738.
David.
> Cheers,
> Tiago
>
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> Tiago de Paula Peixoto <[hidden email]
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> Tiago de Paula Peixoto <[email protected]>
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