o 0 again
  const hideTooltip = function(event,d) {
    tooltip
      .transition()
      .duration(100)
      .style("opacity", 0)
  }

  // append the bar rectangles to the svg element
  svg.selectAll("rect")
      .data(bins)
      .join("rect")
        .attr("x", 1)
        .attr("transform", function(d) { return `translate(${x(d.x0)}, ${y(d.length)})`})
        .attr("width", function(d) { return x(d.x1) - x(d.x0) -1 ; })
        .attr("height", function(d) { return height - y(d.length); })
        .st