Re: [igraph] listing edges connecting nodes with same attributes

[Tamas Nepusz]

Hello,

Use the "%--%" operator when indexing the edge sequence; see this page
for more details (under the heading "Special functions"):

http://igraph.org/r/doc/igraph-es-indexing.html

Example:

g <- grg.game(100, 0.2)
V(g)$color <- c("red", "green")
E(g)[V(g)$color == "red" %--% V(g)$color == "red"]

This will give you all the edges between red nodes; you can then use
length() to figure out how many such edges there are.

T.


On Tue, Oct 11, 2016 at 11:52 AM, Luca Rossi <address@hidden> wrote:
> Hello,
>
> I’m sure this is a very simple question but for some reason I can’t figure 
> out how to do it.
> I need to list all the edges connecting nodes with a specific attribute. 
> (e.g. nodes can be “red” or “green”). So i want to now how many dyads 
> red-red, red-green, green-green.
> I’ve tried with edge_connectivity but it doesn’t work when source and target 
> are the same node (as it happens in this case:
>
>  edge_connectivity(g,source = V(g)[V(g)$color == "green"],target = 
> V(g)[V(g)$color=="green”])
>
>
> is there any way to do this?
>
> Thank you !
>
> Luca
>
>
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