 // Add Y axis
  const y = d3.scaleLinear()
    .domain([0, 100])
    .range([ height, 0 ]);
  svg.append("g")
    .call(d3.axisLeft(y));

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

  // Normalize the data -> sum of each group must be 100!
  console.log(data)
  dataNormalized = []
  data.forEach(function(d){
    // Compute the total
    tot = 0
    for (i in subgroups){ name=subgroups[i] ; tot += +d[name] 