0px
      .padding([0.2])
  svg.append("g")
    .attr("transform", "translate(0," + height + ")")
    .call(d3.axisBottom(x).tickSizeOuter(0));

  // Add Y axis
  var y = d3.scaleLinear()
    .domain([0, 200])
    .range([ height, 0 ]);
  svg.append("g")
    .call(d3.axisLeft(y));

  // color palette
  var color = d3.scaleOrdinal()
    .domain(subgroups)
    .range(['#e41a1c','#377eb8','#4daf4a'])

  // Need to nest = group the data first.
  var nestedData = d3.nest()
    .key(function(d) { return d.group; 