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

Gabor Grothendieck ggrothendieck at gmail.com
Thu Jul 6 03:33:20 CEST 2006

```Try this:

eAttrs <- list(color = c("A~B" = "green", "B~C" = "green", "C~D" = "yellow",
"A~C" = "yellow"))
plot(G, "neato", nodeAttrs = nAttrs, edgeAttrs = eAttrs)

vignette("Rgraphviz")

On 7/5/06, Søren Højsgaard <Soren.Hojsgaard at agrsci.dk> wrote:
> 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)
>
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