Collapse nodes in the circular chart

[radio]

Hi all,

I am looking for a circular chart and casually I found that one http://mbostock.github.com/d3/ex/tree.html 

It has all what I need but I would like to collapse and to show nodes like do this one http://mbostock.github.com/d3/talk/20111018/tree.html

anyone has developed something like that?

Thanx to all in advances