circles.js

circles = svg.selectAll('.ranks')
                   .data(percentileData)
                   .enter()
                   .append('circle')
                      .attr('class', 'ranks')
                      .attr('cx', d => d.cx + 10 )
                      .attr('cy', d => d.cy )
                      .attr('r', d => 10)
                      .attr('fill', d => d3.interpolateRdBu(1-(Math.floor((d.cx/150)*100) / 100)))
                      .attr('stroke', 'black');