[igraph] Problem with attributes

[David Edwards]

Hi

I need to display directed graphs so that any reciprocal edge-pairs are plotted 
without arrows. The code

em1 <- c(0,0,1,1,1,0,1,1,1,1,0,1,1,1,1,0); dim(em1)<- c(4,4)
iG <- graph.adjacency(em1)
E(iG)$arrow.mode <- 2
E(iG)[is.mutual(iG)]$arrow.mode <- 0
iG$layout <- layout.graphopt
plot(iG)

works fine but when I change the graph slightly using instead

em1 <- c(0,1,1,1,1,0,1,1,1,1,0,1,1,1,1,0); dim(em1)<- c(4,4)

(which is symmetric, so all edges are reciprocal), plot gives the warning

Warning messages:
1: In if (code %in% c(2, 3)) { :
  the condition has length > 1 and only the first element will be used
2: In if (code %in% c(1, 3)) { :
  the condition has length > 1 and only the first element will be used

which I don't understand. What am I doing wrong?

Best regards,
David Edwards