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## [igraph] pagerank implementation questions

 From: stainless steel some one Subject: [igraph] pagerank implementation questions Date: Sun, 4 Mar 2007 17:41:03 -0800 (PST)

```I didn't dig deep into the source code, but I have
some questions:

1) Should the range of the damping factor be [0, 1],
i.e. damping could take == 0, or == 1.0, the boundary
value?

and src/structural_properties.c: line 1682 be changed
to:

if (damping< 0 || damping> 1) IGRAPH_ERROR("Invalid
damping factor", IGRAPH_EINVAL);

I made changed, and did some test: the first example
output of: examples/simple/igraph_pagerank.c

passing damping = 1.0, output: 0.00 0.00 0.00 0.00
passing damping = 0.0, output: 1.00 1.00 1.00 1.00

But by the formula on
http://en.wikipedia.org/wiki/PageRank

damping = 0.0, output all should be 1/N = 0.25?
damping = 1.0, output should be sum(pr(x)/l(x))?

2) in the examples/simple/igraph_pagerank.c, is there
any way I can specify weight of each edge? (not just
connectivity, but also the *weight* of each edge?)

3) how the pagerank calculation is actually
implemented?

-- is it by performing (niter) number of iterations?
-- or by solving the eigenvector of the adjacency
matrix?

I suspect it's done by iterations; if this is true, is
there any plan to actual solve the eigenvector of the

Thanks!

-- Judging people by the non/sense he makes, not the name he bears.
-- intelligence = openminded + compassionate

"I don't see why the sex of the candidate is relevant -- this is after all an
academic institution not a bath house!" -- Hilbert on Noether's not being
offered a professorship from University of GĂ¶ttingen.

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```