How to Generate Random Nodes in NS2

I've been trying to get NS2 to generate random nodes, finally, this tcl code seems to work nicely:

set rng [new RNG]
$rng seed next-substream

for {set i 0} {$i < $val(nn)} {incr i} {
    set n($i) [$ns node]
    $n($i) set X_ [$rng uniform 0.0 500.0]
    $n($i) set Y_ [$rng uniform 0.0 500.0]
    $n($i) set Z_ 0.0 #flat ground
    $ns initial_node_pos $n($i) 20
}