data.json

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}

index.html

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<meta charset="utf-8">
<style>

.links line {
  stroke: #999;
  stroke-opacity: 0.6;
}

.nodes circle {
  stroke: #fff;
  stroke-width: 1.5px;
}

</style>
<svg width="960" height="600"></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>
    // https://bl.ocks.org/RobinL/8174dec97312214594084755f6f65096

var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");

var color = d3.scaleOrdinal(d3.schemeCategory20);

var simulation = d3.forceSimulation()
    .force("link", d3.forceLink().id(function(d) { return d.id; }))
    .force("charge", d3.forceManyBody())
    .force("center", d3.forceCenter(width / 2, height / 2));

d3.json("data.json", function(error, graph) {
    if (error) throw error;

    var link = svg.append("g")
        .attr("class", "links")
        .selectAll("line")
        .data(graph.links)
        .enter().append("line")
        .attr("stroke-width", function(d) { return Math.sqrt(d.str); });


    var node = svg.append("g")
        .attr("class", "nodes")
        .selectAll("circle")
        .data(graph.nodes)
        .enter().append("circle")
        .style("opacity", function(d) { return d.size /  20; })
        .attr("r", 5)
        .attr("fill", function(d) { return color(d.size); })
        .call(d3.drag()
            .on("start", dragstarted)
            .on("drag", dragged)
            .on("end", dragended));





  node.append("title")
      .text(function(d) { return d.id; });

  simulation
      .nodes(graph.nodes)
      .on("tick", ticked);

  simulation.force("link")
      .links(graph.links);

  function ticked() {
    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('r', function(d) { return d.size; })
        .attr("cx", function(d) { return d.x; })
        .attr("cy", function(d) { return d.y; });
  }
});

function dragstarted(d) {
  if (!d3.event.active) simulation.alphaTarget(0.3).restart();
  d.fx = d.x;
  d.fy = d.y;
}

function dragged(d) {
  d.fx = d3.event.x;
  d.fy = d3.event.y;
}

function dragended(d) {
  if (!d3.event.active) simulation.alphaTarget(0);
  d.fx = null;
  d.fy = null;
}

</script>