layout.reingold.tilford places two nodes on the same position

[Michal Burda]

In some historical version of igraph (newest in january 2011), the following simple graph was drawn correctly:

 m <- matrix(c(0,0,1,1,0, 0,0,0,1,0, 0,0,0,0,0, 0,0,0,0,0, 0,0,1,1,0), nrow=5)
 g <- graph.adjacency(m)
 plot(g, layout=layout.reingold.tilford)

Igraph version 0.6 places vertices "3" and "4" on the same coordinates:

> layout.reingold.tilford(g)
     [,1] [,2]
[1,] -1 0
[2,] 0 0
[3,] 0 1
[4,] 0 1
[5,] 1 0

[Gábor Csárdi (gabor.csardi)]

I am not sure why this happens, but a possible workaround is to explicitly give the root vertices:

 m <- matrix(c(0,0,1,1,0, 0,0,0,1,0, 0,0,0,0,0, 0,0,0,0,0, 0,0,1,1,0), nrow=5)
 g <- graph.adjacency(m)
 plot(g, layout=layout.reingold.tilford(g, root=c(3,4)))

[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/465