Some visualizations seem to be more sophisticated (to implement) than they actual are, specifically the radial projections. Starting from a tree representation with nodes and links it is quite easy to get to the radial version.
Remark: Of course there are more challenging radial diagrams like the bundle, but lets get started with something simple first !
(I added few more nodes to make the visual difference more obvious)
We change 1 line of our sourcecode (see previous tutorial for complete code):
var tree = d3.layout.tree().size([300,300]); to var tree = d3.layout.cluster().size([300,300]);