Ordinal Axis Grouping 2

Grouping of an ordinal scale not using the axis component

In response to: http://stackoverflow.com/questions/25913528/add-second-x-axis-to-scatterplot-to-display-group-information

<!DOCTYPE html>
<meta charset="utf-8">
<body>
<script src="https://d3js.org/d3.v3.min.js"></script>
<style>
  text {
    font: 12px sans-serif;
  }
  .axis path, .axis line, g.chartGroup path {
    fill: none;
    stroke: #000;
    shape-rendering: crispEdges;
  }
  circle.point {
    fill: steelblue;
    stroke: black;
  }
</style>
<script>

var margin = {top: 10, right: 10, bottom: 30, left: 30},
    width = 500 - margin.left - margin.right,
    height = 300 - margin.top - margin.bottom,
    offset = 7;

var chartData = [
  {name: "AB", group: "A", number: 0.5},
  {name: "ABC", group: "A", number: 10.0},
  {name: "BC", group: "B", number: 3.0},
  {name: "BCD", group: "B", number: 5.0},
  {name: "BCDE", group: "B", number: 0.3},
  {name: "CD", group: "C", number: 1.6},
  {name: "DE", group: "D", number: 1.5}
];

var x = d3.scale.ordinal()
      .domain(chartData.map(function(d) { return d.name; }))
      .rangePoints([0, width]);

var chartGroups = [];
chartData.forEach(function(d, i, array) {
  if (i === 0) d.first = true; else if (d.group !== array[i - 1].group) d.first = true;
  if (i === array.length - 1) d.last = true; else if (d.group !== array[i + 1].group) d.last = true;
  if (d.first) chartGroups.push({
    group: d.group,
    start: i === 0 ? x(d.name) : ((x(d.name) + x(array[i - 1].name)) / 2)
  });
  if (d.last) chartGroups[chartGroups.length - 1].end =
    i === array.length - 1 ? x(d.name) : ((x(d.name) + x(array[i + 1].name)) / 2);
});

var y = d3.scale.linear()
      .domain([0, d3.max(chartData, function(d) { return d.number; })])
      .range([height, 0]),
    xAxis = d3.svg.axis()
      .scale(x)
      .tickValues([])
      .outerTickSize(offset)
      .orient("bottom"),
    yAxis = d3.svg.axis()
      .scale(y)
      .orient("left");

var svg = d3.select("body")
  .append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

svg.selectAll("circle.point")
    .data(chartData)
  .enter().append("circle")
    .attr({
      "class": "point",
      cx: function(d) { return x(d.name); },
      cy: function(d) { return y(d.number); },
      r: 5
    });

svg.append("g")
    .attr("class", "x axis")
    .attr("transform", "translate(0," + height + ")")
    .call(xAxis);

svg.append("g")
    .attr("class", "y axis")
    .call(yAxis);

</script>

Modified http://d3js.org/d3.v3.min.js to a secure url

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