iz")
    .append("div")
      .style("opacity", 0)
      .attr("class", "tooltip")
      .style("font-size", "16px")
  // Three function that change the tooltip when user hover / move / leave a cell
  var mouseover = function(d) {
    tooltip
      .transition()
      .duration(200)
      .style("opacity", 1)
    tooltip
        .html("<span style='color:grey'>Sepal length: </span>" + d.Sepal_Length) // + d.Prior_disorder + "<br>" + "HR: " +  d.HR)
        .style("left", (d3.mouse(this)[0]+30) + "px")
     