How to adjust community border width?

[petershan1119]

I am just wondering how the border width for the groups is adjusted in igraph in R. As shown below, I made an example graph with walktrap community detection, and would like to plot the graph with community borders, but I have no idea how to adjust the community border width (like the one for adjusting edge with: edge.width). I tried to find any information via igraph manual, but there is no information how to adjust the community border with other than the ones for community group shape or community expand options. Thank you in advance!

library(igraph)

# Generate random graph and community structure
set.seed(23)
g <- sample_gnm(15, 45)
wc <- walktrap.community(g)

# Plot
layout <-layout.fruchterman.reingold(g)
plot(wc, g, layout=layout, vertex.label=NA,
     vertex.size=5, edge.arrow.size=.2,
     mark.shape=0, edge.width=0.1, mark.expand=10)