Modify d3 force directed graph

    .force("link", d3.forceLink().id(function(d) { return d.id; }).distance(300).strength(0.5))
//    .force("link", d3.forceLink().id(function(d) { return d.id; }))

http://stackoverflow.com/questions/39244186/how-do-you-set-a-fixed-link-distance-with-d3-v4

https://github.com/d3/d3-force



change the lines in " var nodevar"

//    .enter().append("circle")
//      .attr("r", 5)
     .enter().append("ellipse")
      .attr("rx", 60)
      .attr("ry", 15)

//    .enter().append("circle")