Re: [igraph] igraph.community_fastgreedy method and isolated vertices

[Tamas Nepusz]

Hi,

> its falling over. I suspect its because of isolated vertices (not
> connected to any other nodes) in my graph.
Graph.community_fastgreedy used to fail when executed on non-simple  
graphs or graphs with isolated vertices. Theoretically this bug is  
corrected in the dev tree (and will be corrected in the upcoming  
0.5.1). Anyway, if you could send me an example graph so I could test  
it in the dev tree, that would be great.

> I tried to remove them using the following code
Try this:

isolates = g.vs.select(_degree=0)
g.delete_vertices(isolates)

Your code didn't work because igraph reindexes the vertices when you  
delete one. Alternatively, you can collect isolate vertex indices  
first and delete them in one step:

isolates = [index for index, degree in enumerate(g.degree()) if degree  
== 0]
g.delete_vertices(isolates)

--
T.