code: function() {
          var me = this,
              chart = me.chart,
              store = chart.getChartStore(),
              data = store.data.items,
              count = me.getRecordCount(),
              i, ln, record,
              min, max,
              xField = me.xField,
              xValue;
  
          if (count > 0) {
              min = Infinity;
              max = -min;
                  
              for (i = 0, ln = data.length; i < ln; i++) {
                  record = data[i];
                  xValue = record.get(xField);
                  if (xValue > max) {
                      max = xValue;
                  }
                  if (xValue < min) {
                      min = xValue;
                  }
              }
              
              // If we made no progress, treat it like a category axis
              if (min == Infinity) {
                  min = 0;
              }
              
              if (max == -Infinity) {
                  max = count - 1;
              }
          } else {
              min = max = 0;
          }
          return [min, max];
      }
docs: Calculate the min and max values for this series's xField.
  @return {Array} [min, max]