[R] polygon circling a graph

[email]

Hi:

I want to create a polygon encircling a graph. For this i use convex
hull  to get the coordinate points for polygon.

g <- barabasi.game(10)
L<-layout.fruchterman.reingold(g)
temp1 <- chull(L)
temp1 <- c(temp1, temp1[1])
plot(g, layout=layout.fruchterman.reingold)


But when i plot the polygon with the code below, the polygon dosen't
encircle the graph.

polygon(L[temp1, ], col = "#0000FFAA")

How can I plot a polygon circling a graph?

Regards:
John