eturn +d.price })
      .range([0, width]);
  svg.append("g")
      .attr("transform", "translate(0," + height + ")")
      .call(d3.axisBottom(x));

  // set the parameters for the histogram
  var histogram = d3.histogram()
      .value(function(d) { return d.price; })   // I need to give the vector of value
      .domain(x.domain())  // then the domain of the graphic
      .thresholds(x.ticks(70)); // then the numbers of bins

  // And apply this function to data to get the bins
  var bins = histogram(dat