# [R] Rgraphviz: How to control the colours of edges in a graph

Søren Højsgaard Soren.Hojsgaard at agrsci.dk
Thu Jul 6 02:21:43 CEST 2006

```Using Rgraphviz, I draw the undirected graph with vertices A,B,C and D and edges A:B, B:C, C:D, D:A, A:C. I want the vertices A and B to be red and C and D to be blue. The problem is the following: I want the edges A:B and B:C to be green and the edges C:D and C:A to be yellow, while the edge A:C can have the default colour black. I assume that I have to specify this using the edgeAttrs-argument in the plot function, but I can't figure out how. Can anyone help?
Thanks.
Søren

Code for drawing the graph:

library(Rgraphviz)
V <- c("A","B","C","D")
E <- list(c("A","B"),c("B","C"),c("C","D"),c("D","A"),c("A","C"))
Eidx <- lapply(E, match, V)
edL <- vector("list", length=length(V))
names(edL) <- V
for (i in 1:length(Eidx)){
tmp <- Eidx[[i]]
print(tmp)
edL[[tmp[1]]]\$edges <- c(edL[[tmp[1]]]\$edges, tmp[2])
edL[[tmp[2]]]\$edges <- c(edL[[tmp[2]]]\$edges, tmp[1])
}
G <- new("graphNEL", nodes=V, edgeL=edL)
nAttrs <- list()
nAttrs\$fillcolor <- c("red","red","blue","blue")
names(nAttrs\$fillcolor) <- V
plot(G, "neato",nodeAttrs=nAttrs)

```