code: function buildScales() {
              const decidedRange = isReverse ? [chartWidth, 0] : [0, chartWidth];
  
              xScale = d3Scale.scaleLinear()
                  .domain([0, Math.max(ranges[0], markers[0], measures[0])])
                  .rangeRound(decidedRange)
                  .nice();
  
              // Derive width scales from x scales
              barWidth = bulletWidth(xScale);
  
              // set up opacity scale based on ranges and measures
              rangeOpacityScale = ranges.map((d, i) => startMaxRangeOpacity - (i * rangeOpacifyDiff)).reverse();
              measureOpacityScale = ranges.map((d, i) => 0.9 - (i * measureOpacifyDiff)).reverse();
  
              // initialize range and measure bars and marker line colors
              rangeColor = colorSchema[0];
              measureColor = colorSchema[1];
          }
docs: Creates the x scales of the chart
  @return {void}
  @private