raphic
      .thresholds(x.ticks(70)); // then the numbers of bins

  // And apply this function to data to get the bins
  const bins = histogram(data);

  // Y axis: scale and draw:
  const y = d3.scaleLinear()
      .range([height, 0]);
      y.domain([0, d3.max(bins, function(d) { return d.length; })]);   // d3.hist has to be called before the Y axis obviously
  svg.append("g")
      .call(d3.axisLeft(y));

  // Add a tooltip div. Here I define the general feature of the tooltip: stuff that do not depend