code: protected XYChartData createChartData() {
          XYChartData chartData = new XYChartData(getDataTable());
          if (categoriesColumn != null) {
              if (!seriesColumnList.isEmpty()) {
                  chartData.setCategoryAxisProperty(categoriesColumn.columnId);
                  for (int i=0; i<seriesColumnList.size(); i++) {
                      Column dataColumn = seriesColumnList.get(i);
                      String columnId = dataColumn.columnId;
                      String columnName = dataColumn.columnName;
  
                      XYChartSeries series = new XYChartSeries(columnName, getSeriesColor(i), columnId);
                      chartData.addSeries(series);
                  }
              } else {
                  GWT.log("No values columns specified.");
              }
          } else {
              GWT.log("No categories column specified.");
          }
          return chartData;
      }
docs: Data generation