Re: [igraph] How to plot graph and adjusted community detection (R)?

[Tamas Nepusz]

> The 20 nodes were split into three communities. I wrote the numbers of
> communities to the vector commajd, then compute the function
> modularity() again. Btw, results are different: 0.2573302 - 0.25 =
> 0.0073302, may be  I made an error in vector.
No, the vector is correct; you can check it by extracting the same
membership vector from your "comm" object with:

> membership(comm)
 [1] 1 1 1 2 3 2 1 1 2 2 3 2 1 3 2 2 2 3 3 2

The problem is that "optimal.community" always treats the input graph
as undirected, even when it is directed, as stated in its
documentation. (Maybe it would be wise to give a warning in such
cases). The results are undefined if your input graph is directed.

> Could someone please say me how to plot the origin graph g and new
> community detection commajd together?
Maybe there's a better way (I'm not that familiar with the R
interface), but you can mutate your existing "communities" object:

> comm$membership <- commajd
> plot(comm)

T.