[R] Using igraph: community membership of components built by decompose.graph()

[Natalia Pobedina]

Hi everyone!

I would appreciate help with using decompose.graph(), community
detection functions from igraph and lapply().

I have an igraph object G with vertex attribute "label" and edge
attribute "weight". I want to calculate community
memberships using different functions from igraph, for simplicity let
it be "walktrap.community".
This graph is not connected, that is why I decided to decompose it
into connected components and run
 "walktrap.community" on each component, and afterwards add a
community membership vertex attribute to the
original graph G.

I am doing currently the following

comps <- decompose.graph(G,min.vertices=2)
communities <- lapply(comps,walktrap.community)

At this point I get stuck since I get the list object with the
structure I cannot figure out. The documentation on
"decompose.graph" tells only that it returns list object, and when I
use "lapply" on the result I get completely
confused in the results. Moreover, the communities are numbered from 0
in each component, and I don't know
how to supply "weights" parameter into "walktrap.community" function.

If it were not for the components, I would have done the following:
wt <- walktrap.community(G, modularity=TRUE, weights=E(G)$weight)
wmemb <- community.to.membership(G, wt$merges,
                                steps=which.max(wt$modularity)-1)
V(G)$"walktrap" <- wmemb$membership

Could anyone please help me solve this issue? Or provide some
information/links which could help?

Thanks and best wishes,
Natalia