docs: function(datasetIndex) {
  			var barIndex = 0;
  			var meta, j;
  
  			for (j = 0; j < datasetIndex; ++j) {
  				meta = this.chart.getDatasetMeta(j);
  				if (meta.bar && this.chart.isDatasetVisible(j)) {
  					++barIndex;
  				}
  			}
  
  			return barIndex;
  		}