Try this: E(g)[which(V(g)$color == "red") %--% which(V(g)$color == "red")]
This seems to work for me - just tried it in R. T. On Fri, Oct 14, 2016 at 11:37 PM, Luca Rossi <l...@itu.dk> wrote: > Thank you Tamas! > > I've tried what you suggested (it looks exactly what I was looking for) but > for some reason it gives me an error: > Error: unexpected '==' in "E(g)[V(g)$color == "red" %--% V(g)$color ==" > > I really don't understand what's wrong... > > l. > > > ________________________________________ > From: igraph-help <igraph-help-bounces+lucr=itu...@nongnu.org> on behalf of > Tamas Nepusz <nta...@rmki.kfki.hu> > Sent: 11 October 2016 17:09 > To: Help for igraph users > Subject: Re: [igraph] listing edges connecting nodes with same attributes > > 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)$color == "red"] > > This will give you all the edges between red nodes; you can then use > length() to figure out how many such edges there are. > > T. > > > On Tue, Oct 11, 2016 at 11:52 AM, Luca Rossi <l...@itu.dk> wrote: >> Hello, >> >> I’m sure this is a very simple question but for some reason I can’t figure >> out how to do it. >> I need to list all the edges connecting nodes with a specific attribute. >> (e.g. nodes can be “red” or “green”). So i want to now how many dyads >> red-red, red-green, green-green. >> I’ve tried with edge_connectivity but it doesn’t work when source and target >> are the same node (as it happens in this case: >> >> edge_connectivity(g,source = V(g)[V(g)$color == "green"],target = >> V(g)[V(g)$color=="green”]) >> >> >> is there any way to do this? >> >> Thank you ! >> >> Luca >> >> >> _______________________________________________ >> igraph-help mailing list >> igraph-help@nongnu.org >> https://lists.nongnu.org/mailman/listinfo/igraph-help > > _______________________________________________ > igraph-help mailing list > igraph-help@nongnu.org > https://lists.nongnu.org/mailman/listinfo/igraph-help > _______________________________________________ > igraph-help mailing list > igraph-help@nongnu.org > https://lists.nongnu.org/mailman/listinfo/igraph-help _______________________________________________ igraph-help mailing list igraph-help@nongnu.org https://lists.nongnu.org/mailman/listinfo/igraph-help
