gistfile1.js

		function tick(e) {
			node.each(gravity(.2 * e.alpha))
				.each(collide(.3))
				.attr("cx", function(d) { return d.x; })
				.attr("cy", function(d) { return d.y; })
				.attr("transform", function(d) {
					return "translate(" + d.x + "," + d.y + ")";
				});
			}

		d3.select("#sort")
			.on("click", function(d,i) {

			});

		function gravity(alpha) {
			return function(d) {
				d.y += (d.cy - d.y) * alpha;
				d.x += (d.cx - d.x) * alpha;
			};
		}