anchor.diff:    }
   
     // Toggle children on click.
  -  function click(d) {
  +  function toggle(d) {
       if (d.children) {
         d._children = d.children;
         d.children = null;
  
positive.code:         .attr("cy", function(d) { return d.y; })
          .attr("r", function(d) { return Math.sqrt(d.size) / 10 || 4.5; })
          .style("fill", color)
          .on("click", click)
          .call(force.drag);
  
      // Exit any old nodes.
  
negative.code:   d3.json("visualisation-example-data.json", function(json) {
      root = json;
      update();
  
      // Initialize the display to show a few nodes.
      // from: http://stackoverflow.com/questions/17504136/starting-d3-force-layout-collapsed-text-labels-duplicating
      function collapseAll(d) {
          if (d.children) {
            d.children.forEach(collapseAll);
            toggle(d);
          }
        }
        root.children.forEach(collapseAll);
        update(root);
  
    });
  
    function update() {
  