Collapsible/hierarchical AND force-directed graph in d3.js

Question

There are numerous examples of force-directed graphs (i.e. nodes and links) and collapsible trees (i.e. parent-child nodes) but I cant find an example of the combination of thes

Answer 1

i try to merge both examples here my fiddle

// Toggle children on click.
function click(d) {
if (d.children) {
    d._children = d.children;
    d.children = null;
} else {
    d.children = d._children;
    d._children = null;
}
update();
}