code: function (d, chart, series) {
              var returnR = 0;
              if (series.z === null || series.z === undefined) {
                  returnR = 5;
              } else if (series.z._hasMeasure()) {
                  returnR = series.z._scale(d.r);
              } else {
                  returnR = series.z._scale(chart._heightPixels() / 100);
              }
              return returnR;
          }
docs: Calculate the radius