[igraph] listing edges connecting nodes with same attributes

[Luca Rossi]

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