title: how to prevent overlapping of link in force directed graph?
body: <p>I am following <a href="http://bl.ocks.org/mbostock/4062045" rel="noreferrer">Force directed Graph</a>. How to prevent overlapping of link (line) in force directed graph. Expected output should be like 
   <a href="https://i.stack.imgur.com/f6F2G.png" rel="noreferrer">this</a>. Current JSON data does not contain any parent child relation ship.</p>
  
  <p>Here is my Code:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="false" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var width = 960,
      height = 500;
  
  var color = d3.scale.category20();
  
  var force = d3.layout.force()
      .charge(-120)
      .linkDistance(30)
      .size([width, height]);
  
  var svg = d3.select("body").append("svg")
      .attr("width", width)
      .attr("height", height);
  
  var graph = {
    "nodes":[
      {"name":"Myriel","group":1},
      {"name":"Napoleon","group":1},
      {"name":"Mlle.Baptistine","group":1},
      {"name":"Mme.Magloire","group":1},
      {"name":"CountessdeLo","group":1},
      {"name":"Geborand","group":1},
      {"name":"Champtercier","group":1},
      {"name":"Cravatte","group":1},
      {"name":"Count","group":1},
      {"name":"OldMan","group":1},
      {"name":"Labarre","group":2},
      {"name":"Valjean","group":2},
      {"name":"Marguerite","group":3},
      {"name":"Mme.deR","group":2},
      {"name":"Isabeau","group":2},
      {"name":"Gervais","group":2},
      {"name":"Tholomyes","group":3},
      {"name":"Listolier","group":3},
      {"name":"Fameuil","group":3},
      {"name":"Blacheville","group":3},
      {"name":"Favourite","group":3},
      {"name":"Dahlia","group":3},
      {"name":"Zephine","group":3},
      {"name":"Fantine","group":3},
      {"name":"Mme.Thenardier","group":4},
      {"name":"Thenardier","group":4},
      {"name":"Cosette","group":5},
      {"name":"Javert","group":4},
      {"name":"Fauchelevent","group":0},
      {"name":"Bamatabois","group":2},
      {"name":"Perpetue","group":3},
      {"name":"Simplice","group":2},
      {"name":"Scaufflaire","group":2},
      {"name":"Woman1","group":2},
      {"name":"Judge","group":2},
      {"name":"Champmathieu","group":2},
      {"name":"Brevet","group":2},
      {"name":"Chenildieu","group":2},
      {"name":"Cochepaille","group":2},
      {"name":"Pontmercy","group":4},
      {"name":"Boulatruelle","group":6},
      {"name":"Eponine","group":4},
      {"name":"Anzelma","group":4},
      {"name":"Woman2","group":5},
      {"name":"MotherInnocent","group":0},
      {"name":"Gribier","group":0},
      {"name":"Jondrette","group":7},
      {"name":"Mme.Burgon","group":7},
      {"name":"Gavroche","group":8},
      {"name":"Gillenormand","group":5},
      {"name":"Magnon","group":5},
      {"name":"Mlle.Gillenormand","group":5},
      {"name":"Mme.Pontmercy","group":5},
      {"name":"Mlle.Vaubois","group":5},
      {"name":"Lt.Gillenormand","group":5},
      {"name":"Marius","group":8},
      {"name":"BaronessT","group":5},
      {"name":"Mabeuf","group":8},
      {"name":"Enjolras","group":8},
      {"name":"Combeferre","group":8},
      {"name":"Prouvaire","group":8},
      {"name":"Feuilly","group":8},
      {"name":"Courfeyrac","group":8},
      {"name":"Bahorel","group":8},
      {"name":"Bossuet","group":8},
      {"name":"Joly","group":8},
      {"name":"Grantaire","group":8},
      {"name":"MotherPlutarch","group":9},
      {"name":"Gueulemer","group":4},
      {"name":"Babet","group":4},
      {"name":"Claquesous","group":4},
      {"name":"Montparnasse","group":4},
      {"name":"Toussaint","group":5},
      {"name":"Child1","group":10},
      {"name":"Child2","group":10},
      {"name":"Brujon","group":4},
      {"name":"Mme.Hucheloup","group":8}
    ],
    "links":[
      {"source":1,"target":0,"value":1},
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      {"source":76,"target":48,"value":1},
      {"source":76,"target":58,"value":1}
    ]
  }
  
  //d3.json("miserables.json", function(error, graph) {
    force
        .nodes(graph.nodes)
        .links(graph.links)
        .start();
  
    var link = svg.selectAll(".link")
        .data(graph.links)
      .enter().append("line")
        .attr("class", "link")
        .style("stroke-width", function(d) { return Math.sqrt(d.value); });
  
    var node = svg.selectAll(".node")
        .data(graph.nodes)
      .enter().append("circle")
        .attr("class", "node")
        .attr("r", 5)
        .style("fill", function(d) { return color(d.group); })
        .call(force.drag);
  
    node.append("title")
        .text(function(d) { return d.name; });
  
    force.on("tick", function() {
      link.attr("x1", function(d) { return d.source.x; })
          .attr("y1", function(d) { return d.source.y; })
          .attr("x2", function(d) { return d.target.x; })
          .attr("y2", function(d) { return d.target.y; });
  
      node.attr("cx", function(d) { return d.x; })
          .attr("cy", function(d) { return d.y; });
    });
  //});</code></pre>
  <pre class="snippet-code-css lang-css prettyprint-override"><code>.node {
    stroke: #fff;
    stroke-width: 1.5px;
  }
  
  .link {
    stroke: #999;
    stroke-opacity: .6;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.0/d3.min.js"&gt;&lt;/script&gt;</code></pre>
  </div>
  </div>
  </p>