e")
      .attr("stroke-width", function(d) { return Math.sqrt(d.value); });

  var node = svg.append("g")
      .attr("class", "nodes")
    .selectAll("circle")
    .data(graph.nodes)
    .enter().append("circle")
      .attr("r", 5)
      .attr("fill", function(d) { return color(d.group); })
	  .on("mouseover", function(d) {
            div.transition()
                .duration(200)
                .style("opacity", .9);
            div	.html(d.id)
                .style("left", (d3.event.pageX) + "px")
