Donut Multiples

These donut charts are constructed from a CSV file storing the populations of various age groups in different states. (As a practical note, a normalized stacked area chart facilitates easier comparison of values.) The chart employs a number of D3 features:

d3.csv - load and parse data
d3.scale.ordinal - color encoding
d3.keys - compute column names
d3.svg.arc - display arcs
d3.layout.pie - compute arc angles from data

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

body {
  font: 10px sans-serif;
}

svg {
  padding: 10px 0 0 10px;
}

.arc {
  stroke: #fff;
}

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

var radius = 74,
    padding = 10;

var color = d3.scale.ordinal()
    .range(["#98abc5", "#8a89a6", "#7b6888", "#6b486b", "#a05d56", "#d0743c", "#ff8c00"]);

var arc = d3.svg.arc()
    .outerRadius(radius)
    .innerRadius(radius - 30);

var pie = d3.layout.pie()
    .sort(null)
    .value(function(d) { return d.population; });

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

color.domain(d3.keys(data[0]).filter(function(key) { return key !== "State"; }));

data.forEach(function(d) {
    d.ages = color.domain().map(function(name) {
      return {name: name, population: +d[name]};
    });
  });

var legend = d3.select("body").append("svg")
      .attr("class", "legend")
      .attr("width", radius * 2)
      .attr("height", radius * 2)
    .selectAll("g")
      .data(color.domain().slice().reverse())
    .enter().append("g")
      .attr("transform", function(d, i) { return "translate(0," + i * 20 + ")"; });

legend.append("rect")
      .attr("width", 18)
      .attr("height", 18)
      .style("fill", color);

legend.append("text")
      .attr("x", 24)
      .attr("y", 9)
      .attr("dy", ".35em")
      .text(function(d) { return d; });

var svg = d3.select("body").selectAll(".pie")
      .data(data)
    .enter().append("svg")
      .attr("class", "pie")
      .attr("width", radius * 2)
      .attr("height", radius * 2)
    .append("g")
      .attr("transform", "translate(" + radius + "," + radius + ")");

svg.selectAll(".arc")
      .data(function(d) { return pie(d.ages); })
    .enter().append("path")
      .attr("class", "arc")
      .attr("d", arc)
      .style("fill", function(d) { return color(d.data.name); });

svg.append("text")
      .attr("dy", ".35em")
      .style("text-anchor", "middle")
      .text(function(d) { return d.State; });

});

</script>

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