index.html

## index.html
<!DOCTYPE html>
<html>
  <head>
    <title>Force-Directed Layout (Multiple Foci)</title>
    <script type="text/javascript" src="http://mbostock.github.com/d3/d3.js"></script>
    <script type="text/javascript" src="http://mbostock.github.com/d3/d3.geom.js"></script>
    <script type="text/javascript" src="http://mbostock.github.com/d3/d3.layout.js"></script>
  </head>
  <body>
    <script type="text/javascript">

var w = 960,
    h = 500,
    fill = d3.scale.category10(),
    nodes = [],
    foci = [{x: 150, y: 150}, {x: 350, y: 250}, {x: 700, y: 400}];

var vis = d3.select("body").append("svg:svg")
    .attr("width", w)
    .attr("height", h);

var force = d3.layout.force()
    .nodes(nodes)
    .links([])
    .gravity(0)
    .size([w, h]);

force.on("tick", function(e) {

  // Push nodes toward their designated focus.
  var k = .1 * e.alpha;
  nodes.forEach(function(o, i) {
    o.y += (foci[o.id].y - o.y) * k;
    o.x += (foci[o.id].x - o.x) * k;
  });

  vis.selectAll("circle.node")
      .attr("cx", function(d) { return d.x; })
      .attr("cy", function(d) { return d.y; });
});

setInterval(function(){
  nodes.push({id: ~~(Math.random() * foci.length)});
  force.start();

  vis.selectAll("circle.node")
      .data(nodes)
    .enter().append("svg:circle")
      .attr("class", "node")
      .attr("cx", function(d) { return d.x; })
      .attr("cy", function(d) { return d.y; })
      .attr("r", 8)
      .style("fill", function(d) { return fill(d.id); })
      .style("stroke", function(d) { return d3.rgb(fill(d.id)).darker(2); })
      .style("stroke-width", 1.5)
      .call(force.drag);
}, 1000);

    </script>
  </body>
</html>

## thumbnail.png

      
        

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              thumbnail.png