Symbol Map

The area of each circle in this symbol map is proportional to the population of the associated state.

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.states {
  fill: #ccc;
  stroke: #fff;
}

.symbol {
  fill: steelblue;
  fill-opacity: .8;
  stroke: #fff;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script src="//d3js.org/queue.v1.min.js"></script>
<script>

var width = 960,
    height = 500;

var radius = d3.scale.sqrt()
    .domain([0, 1e6])
    .range([0, 10]);

var path = d3.geo.path();

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

queue()
    .defer(d3.json, "/../../data/us.json")
    .defer(d3.json, "us-state-centroids.json")
    .await(ready);

function ready(error, us, centroid) {
  if (error) throw error;

svg.append("path")
      .attr("class", "states")
      .datum(topojson.feature(us, us.objects.states))
      .attr("d", path);

svg.selectAll(".symbol")
      .data(centroid.features.sort(function(a, b) { return b.properties.population - a.properties.population; }))
    .enter().append("path")
      .attr("class", "symbol")
      .attr("d", path.pointRadius(function(d) { return radius(d.properties.population); }));
}

</script>

Changed /mbostock/raw/4090846/us.json to a local referenece

https://d3js.org/d3.v3.min.js

https://d3js.org/topojson.v1.min.js

https://d3js.org/queue.v1.min.js