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## Re: [igraph] weighted pagerank?

 From: Csardi Gabor Subject: Re: [igraph] weighted pagerank? Date: Sat, 23 Aug 2008 16:02:25 +0200 User-agent: Mutt/1.5.9i

```Eytan,

the difference is more than 50 percent. I guess it would be more
if the weights were not uniformly distributed.

> library(igraph)
> g <- simplify(ba.game(1000, m=5))
> pg1 <- page.rank(g)
> pg2 <- page.rank(g, weights=runif(ecount(g),1,1000))
> max( (pg1\$vector - pg2\$vector) / pg1\$vector)
[1] 0.5442513

Gabor

On Fri, Aug 22, 2008 at 07:18:30PM -0400, Eytan Bakshy wrote:
> Hello,
>
> I am using igraph 0.51 in R and igraph 0.5 in python, and it doesn't
> seem that specifying edge weights has any effect in either
> implementation.  I know that the igraph 0.5 release announcement
> mentions that Page Rank and the fast greedy algorithm supports edge
> weights, but is this just in the C library.
>
> In python, I tried creating several graphs where edges have the
> attribute 'weight', which were floats.  I am trying to compute the
> weighted pagerank by saying:
>       prw = g.pagerank(weights='weight')
>
> and if i do:
>       pr = g.pagerank()
> the following statement yields True:
>       prw == pr
>
> on several graphs using edge weights that were distributed uniformly
> at random between (0,1), and then again between (1,1000)
>
>
> I am pretty new to R, but it appears that the same thing holds using
> page.rank(g, weights=runif(length(E(g)),1,10000))
>
>
> Thanks,
> Eytan
>
>
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