[igraph] making random graphs from matrices

[Robin Cowan]

Dear List,

Is there a simple way of taking a square (symmetric) matrix of reals  
and generating a random graph of fixed density using that matrix as  
the (relative) probability of a particular link forming.

I am using igraph inside R.

It seems one way to do that would be with a two-dimensional version  
of the sample() statement, to create an adjacency matrix, but I can't  
find documentation on that.

It also seems related to igraph's preference.game() but I can't see a  
way there to control density

Thanks for your help.

Robin Cowan