RE: [igraph] threshold

[Harun Pirim]

Thank you very much,
Another question arises about connectivity.
How can I guarantee connectivity for this binary graph, in other words use
determine a threshold optimizing connectivity, strongest 0.2% edges (if
violates connectivity then less stronger edge is chosen) in R?   

-----Original Message-----
From: address@hidden
[mailto:address@hidden On Behalf Of
Gábor Csárdi
Sent: Tuesday, March 30, 2010 2:59 AM
To: Help for igraph users
Subject: Re: [igraph] threshold

On Sun, Mar 28, 2010 at 4:30 PM, Tamas Nepusz <address@hidden> wrote:
> Hi,
>
>> Is there a direct way in iGraph to calculate a threshold that will retain
let's say 2% of the strongest weighted edges and convert a weighted graph to
a binary graph using this threshold ?
> No, since it is only a few lines of code using either the R or the Python
interface. In Python, you can do something like this:
>
> weights = sorted(g.es["weight"], reverse=True)
> threshold = weights[len(weights) * 0.02]
> g.delete_edges(g.es.select(weight_lt = threshold))
> del g.es["weight"]
>
> --
> Tamas
[...]

The same in R:

weights <- sort(E(g)$weight, decreasing=TRUE)
threshold <- weights[length(weights) * 0.02]
g2 <- delete.edges(g, which(E(g)$weight < threshold)-1)
g2 <- remove.edge.attribute(g, "weight")

Gabor

-- 
Gabor Csardi <address@hidden>     UNIL DGM


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