Cannot find API to add error bars using Apache POI - apache-poi

Question

I was trying to find how to add error bars to the scatter plot chart using Apache POI as shown in the picture below. My research could not help me find the corresponding API. Can you please help to find the API.

Answer 1

Adding error bars is not supported by the high level apache poi classes until now. It would must be a method in XDDFChartData.Series.
But *.xlsx files are simply ZIP archives. So we can set the error bars using Excel's GUI. Then unzip the *.xlsx ZIP archive and have a look at /xl/charts/chart1.xml to find what has changed.
We will find something like:
...
<c:ser>
...
<c:errBars>
<c:errDir val="y"/>
<c:errBarType val="both"/>
<c:errValType val="percentage"/>
<c:val val="10.0"/>
</c:errBars>
...
</c:ser>
...
Now we can create that XML using the low level classes of ooxml-schemas:
...
// add error bars
chart.getCTChart().getPlotArea().getScatterChartArray(0).getSerArray(0).addNewErrBars();
// set error bars direction only Y
chart.getCTChart().getPlotArea().getScatterChartArray(0).getSerArray(0).getErrBarsArray(0).addNewErrDir().setVal(
org.openxmlformats.schemas.drawingml.x2006.chart.STErrDir.Y);
// set error bars type to both (minus and plus)
chart.getCTChart().getPlotArea().getScatterChartArray(0).getSerArray(0).getErrBarsArray(0).addNewErrBarType().setVal(
org.openxmlformats.schemas.drawingml.x2006.chart.STErrBarType.BOTH);
// set error bars value type to percentage
chart.getCTChart().getPlotArea().getScatterChartArray(0).getSerArray(0).getErrBarsArray(0).addNewErrValType().setVal(
org.openxmlformats.schemas.drawingml.x2006.chart.STErrValType.PERCENTAGE);
// set error bars value to 10%
chart.getCTChart().getPlotArea().getScatterChartArray(0).getSerArray(0).getErrBarsArray(0).addNewVal().setVal(10d);
...
Complete example:
import java.io.*;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.*;
import org.apache.poi.ss.util.*;
import org.apache.poi.xddf.usermodel.*;
import org.apache.poi.xddf.usermodel.chart.*;
public class ScatterChart {
public static void main(String[] args) throws IOException {
Double[][] data = new Double[][]{
new Double[]{0d, 1d, 2d, 3d, 4d, 5d, 6d, 7d, 8d, 9d},
new Double[]{1.1d, 1.5d, 1.2d, 2.5d, 2.7d, 6.5d, 6.5d, 1.0d, 1.0d, 0.5d},
};
try (XSSFWorkbook wb = new XSSFWorkbook()) {
XSSFSheet sheet = wb.createSheet();
final int NUM_OF_ROWS = data.length;
final int NUM_OF_COLUMNS = data[0].length;
Row row;
Cell cell;
int rowIndex = 0;
int colIndex = 0;
for (Double[] dataRow : data) {
row = sheet.createRow(rowIndex++);
colIndex = 0;
for (Double value : dataRow) {
cell = row.createCell(colIndex++);
cell.setCellValue(value);
}
}
XSSFDrawing drawing = sheet.createDrawingPatriarch();
XSSFClientAnchor anchor = drawing.createAnchor(0, 0, 0, 0, 0, 3, 10, 23);
XSSFChart chart = drawing.createChart(anchor);
XDDFChartLegend legend = chart.getOrAddLegend();
legend.setPosition(LegendPosition.TOP_RIGHT);
XDDFSolidFillProperties gridLinesFill = new XDDFSolidFillProperties(XDDFColor.from(
new byte[]{(byte)230,(byte)230,(byte)230}));
XDDFLineProperties gridLineProperties = new XDDFLineProperties();
gridLineProperties.setFillProperties(gridLinesFill);
XDDFValueAxis bottomAxis = chart.createValueAxis(AxisPosition.BOTTOM);
bottomAxis.setTitle("x");
XDDFShapeProperties shapeProperties = bottomAxis.getOrAddMajorGridProperties();
shapeProperties.setLineProperties(gridLineProperties);
XDDFValueAxis leftAxis = chart.createValueAxis(AxisPosition.LEFT);
leftAxis.setTitle("f(x)");
leftAxis.setCrosses(AxisCrosses.AUTO_ZERO);
shapeProperties = leftAxis.getOrAddMajorGridProperties();
shapeProperties.setLineProperties(gridLineProperties);
XDDFDataSource<Double> xs = XDDFDataSourcesFactory.fromNumericCellRange(
sheet,
new CellRangeAddress(0, 0, 0, NUM_OF_COLUMNS - 1)
);
XDDFNumericalDataSource<Double> ys = XDDFDataSourcesFactory.fromNumericCellRange(
sheet,
new CellRangeAddress(1, 1, 0, NUM_OF_COLUMNS - 1)
);
XDDFScatterChartData chartData = (XDDFScatterChartData) chart.createData(ChartTypes.SCATTER, bottomAxis, leftAxis);
chartData.setVaryColors(false);
XDDFScatterChartData.Series series = (XDDFScatterChartData.Series) chartData.addSeries(xs, ys);
series.setTitle("Series 1", null);
series.setSmooth(false);
chart.plot(chartData);
solidLineSeries(series, PresetColor.BLUE);
// add error bars
chart.getCTChart().getPlotArea().getScatterChartArray(0).getSerArray(0).addNewErrBars();
// set error bars direction only Y
chart.getCTChart().getPlotArea().getScatterChartArray(0).getSerArray(0).getErrBarsArray(0).addNewErrDir().setVal(
org.openxmlformats.schemas.drawingml.x2006.chart.STErrDir.Y);
// set error bars type to both (minus and plus)
chart.getCTChart().getPlotArea().getScatterChartArray(0).getSerArray(0).getErrBarsArray(0).addNewErrBarType().setVal(
org.openxmlformats.schemas.drawingml.x2006.chart.STErrBarType.BOTH);
// set error bars not have no end caps - necessary for current Excel versions
chart.getCTChart().getPlotArea().getScatterChartArray(0).getSerArray(0).getErrBarsArray(0).addNewNoEndCap().setVal(false);
// set error bars value type to percentage
chart.getCTChart().getPlotArea().getScatterChartArray(0).getSerArray(0).getErrBarsArray(0).addNewErrValType().setVal(
org.openxmlformats.schemas.drawingml.x2006.chart.STErrValType.PERCENTAGE);
// set error bars value to 10%
chart.getCTChart().getPlotArea().getScatterChartArray(0).getSerArray(0).getErrBarsArray(0).addNewVal().setVal(10d);
// Write the output to a file
try (FileOutputStream fileOut = new FileOutputStream("ooxml-scatter-chart.xlsx")) {
wb.write(fileOut);
}
}
}
private static void solidLineSeries(XDDFChartData.Series series, PresetColor color) {
XDDFSolidFillProperties fill = new XDDFSolidFillProperties(XDDFColor.from(color));
XDDFLineProperties line = new XDDFLineProperties();
line.setFillProperties(fill);
XDDFShapeProperties properties = series.getShapeProperties();
if (properties == null) {
properties = new XDDFShapeProperties();
}
properties.setLineProperties(line);
series.setShapeProperties(properties);
}
}