R interface: warning when arrow.mode is the same for all edges

[Tamás Nepusz]

This bug was originally reported by David Edwards on the mailing list. The following code reproduces the bug:

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

The bug can be resolved by replacing "code=arrow.mode" with "code=unique(arrow.mode)" in line 225 of plot.R. I'm not sure whether this is the optimal solution, though, so I'm leaving it as a pending bug report for the time being. Gabor, if there is a better solution than this, please commit that to the R interface; otherwise, please commit this.

[Gábor Csárdi (gabor.csardi)]

Yes, this is a correct fix, but arrow.mod[1] is very slightly better, I have committed this into 0.6-main (revision #1967).

[Gábor Csárdi (gabor.csardi)]

The development of igraph has moved to github, so please do not comment on this bug here. You are of course welcome to comment on github, here:
https://github.com/igraph/igraph/issues/275