title: d3 drawing arrows tips
body: <p>In this example : </p>
  
  <p><a href="http://jsfiddle.net/maxl/mNmYH/2/" rel="noreferrer">http://jsfiddle.net/maxl/mNmYH/2/</a></p>
  
  <p>If I enlarge the circles, ex: </p>
  
  <pre><code>var radius = 30; // (is 6 in the jsFiddle)
  var circle = svg.append("svg:g").selectAll("circle")
  .data(force.nodes())
  .enter().append("svg:circle")
  .attr("r", radius)
  </code></pre>
  
  <p>What is the best way to properly adjust the drawing of the arrow
  so that it points to the radius of the circle ? </p>
  
  <p>Thanks</p>