title: Disable node drag in force layout
body: <p>Implemented force layout, here is the <a href="http://jsfiddle.net/8tcd9/6/" rel="nofollow">fiddle</a>. However I want to disable the drag behaviour for the nodes, drag event will move the nodes across and set the nodes center to cursor position until mouseup event. Is there a way we can disable this?  I tried removing the callback from the nodes as follows:</p>
  
  <pre><code>node.append("svg:circle").attr("r",5).style("fill", "#FE9A2E").on("mousedown.drag", null) 
  </code></pre>
  
  <p>This didn't work. not sure if it will remove the callback from the node. also tried fixing the node position on drag event by setting fixed property of the node to true. But that fixes the node after it has been dragged. how can I stop the nodes from dragging?  </p>