[igraph] layout repeatability in R ?

[Olivier Delrieu]

Dear All,

I am wondering how to achieve layout repeatability with igraph in R,
especially with the Kamada-Kawai and Fruchterman-Reingold algorithms? By
this I mean ability to produce the same result given fully specified
starting conditions.

This is quite important when exchanging data & results with other
researchers. Also, Kamada-Kawai can be used for quickly generating an
advantageous initial layout which can be passed to Fruchterman-Reingold
for a visually more significant placement of neighbored nodes.

The code below shows this is not the case with layout.drl despite
providing seed coordinates to the algorithm. Am I missing something?

Regarding Kamada-Kawai, and Fruchterman-Reingold the C++ code shows
initial configuration can be provided with 'use_seed' and 'res', but
these parameters are not documented in the R equivalent. See:
http://igraph.sourceforge.net/doc/html/igraph_layout_kamada_kawai.html
http://igraph.sourceforge.net/doc/html/igraph_layout_fruchterman_reingold.html

http://igraph.sourceforge.net/doc/R/layout.html

R code:

library(igraph)
g <- graph.de.bruijn(5,2)
coord <- layout.kamada.kawai(g)
coord2 <- layout.drl(g, use.seed=TRUE, seed=coord)
coord3 <- layout.drl(g, use.seed=TRUE, seed=coord)
X11()
plot(g,layout=coord2)
X11()
plot(g,layout=coord3)


Many thanks,

Olivier.