code: function (d, chart, series) {
              var returnXClusterGap = 0;
              if (series.x.categoryFields !== null && series.x.categoryFields !== undefined && series.x.categoryFields.length >= 2 && series.clusterBarGap > 0 && !series.x._hasMeasure()) {
                  returnXClusterGap = (d.width * ((chart._widthPixels() / series.x._max) - (dimple._helpers.xGap(chart, series) * 2)) * (series.clusterBarGap > 0.99 ? 0.99 : series.clusterBarGap)) / 2;
              }
              return returnXClusterGap;
          }
docs: Calculate the x gap for clusters within bar type charts