Manage Chart Data Labels in Presentations on Android
Introduction
Data labels display information about chart series and individual data points, helping readers identify values and understand the chart. This article explains how to format values, display percentages, read label text, adjust category axis label spacing, and position pie chart labels.
Set Data Precision in Chart Data Labels
Use setNumberFormatOfValues to format series values. This example creates a line chart with default data, displays its data table, and enables value labels for the first series. The format #,##0.00 displays a thousands separator and two decimal places without changing the underlying values.
import com.aspose.slides.*;
Presentation presentation = new Presentation();
try {
ISlide slide = presentation.getSlides().get_Item(0);
IChart chart = slide.getShapes().addChart(ChartType.Line, 50, 50, 450, 300);
chart.setDataTable(true);
IChartSeries series = chart.getChartData().getSeries().get_Item(0);
series.setNumberFormatOfValues("#,##0.00");
series.getLabels().getDefaultDataLabelFormat().setShowValue(true);
presentation.save("PrecisionOfDatalabels_out.pptx", SaveFormat.Pptx);
} finally {
presentation.dispose();
}
Display Percentages as Labels
For a stacked column chart, calculate each value as a percentage of its category total and assign the text to the text frame returned by getTextFrameForOverriding. This example uses the default chart data and displays percentages with two decimal places in an 8-point font. Categories with a total of zero are skipped to avoid division by zero. Recalculate the custom label text if the chart data changes.
import com.aspose.slides.*;
import java.util.Locale;
Presentation presentation = new Presentation();
try {
ISlide slide = presentation.getSlides().get_Item(0);
IChart chart = slide.getShapes().addChart(ChartType.StackedColumn, 20, 20, 400, 400);
double[] categoryTotals = new double[chart.getChartData().getCategories().size()];
for (int k = 0; k < chart.getChartData().getCategories().size(); k++) {
for (int i = 0; i < chart.getChartData().getSeries().size(); i++) {
IChartSeries series = chart.getChartData().getSeries().get_Item(i);
Number pointValue = (Number) series.getDataPoints().get_Item(k).getValue().getData();
categoryTotals[k] += pointValue.doubleValue();
}
}
for (int x = 0; x < chart.getChartData().getSeries().size(); x++) {
IChartSeries series = chart.getChartData().getSeries().get_Item(x);
series.getLabels().getDefaultDataLabelFormat().setShowLegendKey(false);
for (int j = 0; j < series.getDataPoints().size(); j++) {
IDataLabel label = series.getDataPoints().get_Item(j).getLabel();
if (categoryTotals[j] == 0) {
continue;
}
Number pointValue = (Number) series.getDataPoints().get_Item(j).getValue().getData();
double dataPointPercent = (pointValue.doubleValue() / categoryTotals[j]) * 100;
IPortion portion = new Portion();
portion.setText(String.format(Locale.US, "%.2f %%", dataPointPercent));
portion.getPortionFormat().setFontHeight(8f);
label.getTextFrameForOverriding().setText("");
IParagraph paragraph = label.getTextFrameForOverriding().getParagraphs().get_Item(0);
paragraph.getPortions().add(portion);
label.getDataLabelFormat().setShowValue(true);
label.getDataLabelFormat().setShowSeriesName(false);
label.getDataLabelFormat().setShowPercentage(false);
label.getDataLabelFormat().setShowLegendKey(false);
label.getDataLabelFormat().setShowCategoryName(false);
label.getDataLabelFormat().setShowBubbleSize(false);
}
}
presentation.save("DisplayPercentageAsLabels_out.pptx", SaveFormat.Pptx);
} finally {
presentation.dispose();
}
Set the Percentage Sign with Chart Data Labels
When values are stored as fractions, use setNumberFormat to display percentages. Pass false to setNumberFormatLinkedToSource to apply the label format independently of the source cells.
This example creates a 100% stacked column chart with red and blue series across four categories. Each pair of values adds up to 1. The label format 0.0% displays 0.30 as 30.0%, while the vertical axis uses two decimal places. Both series use white, 10-point label text.
import com.aspose.slides.*;
import android.graphics.Color;
Presentation presentation = new Presentation();
try {
ISlide slide = presentation.getSlides().get_Item(0);
IChart chart = slide.getShapes().addChart(ChartType.PercentsStackedColumn, 20, 20, 500, 400);
chart.getAxes().getVerticalAxis().setNumberFormatLinkedToSource(false);
chart.getAxes().getVerticalAxis().setNumberFormat("0.00%");
chart.getChartData().getSeries().clear();
chart.getChartData().getCategories().clear();
IChartDataWorkbook workbook = chart.getChartData().getChartDataWorkbook();
int worksheetIndex = 0;
for (int i = 0; i < 4; i++) {
IChartDataCell categoryCell = workbook.getCell(worksheetIndex, i + 1, 0, "Category " + (i + 1));
chart.getChartData().getCategories().add(categoryCell);
}
String[] seriesNames = { "Reds", "Blues" };
int[] seriesColors = { Color.RED, Color.BLUE };
double[][] values = { { 0.30, 0.50, 0.80, 0.65 }, { 0.70, 0.50, 0.20, 0.35 } };
for (int i = 0; i < seriesNames.length; i++) {
IChartDataCell seriesCell = workbook.getCell(worksheetIndex, 0, i + 1, seriesNames[i]);
IChartSeries series = chart.getChartData().getSeries().add(seriesCell, chart.getType());
for (int j = 0; j < 4; j++) {
IChartDataCell valueCell = workbook.getCell(worksheetIndex, j + 1, i + 1, values[i][j]);
series.getDataPoints().addDataPointForBarSeries(valueCell);
}
series.getFormat().getFill().setFillType(FillType.Solid);
series.getFormat().getFill().getSolidFillColor().setColor(seriesColors[i]);
IDataLabelFormat labelFormat = series.getLabels().getDefaultDataLabelFormat();
labelFormat.setShowValue(true);
labelFormat.setNumberFormatLinkedToSource(false);
labelFormat.setNumberFormat("0.0%");
labelFormat.getTextFormat().getPortionFormat().setFontHeight(10);
labelFormat.getTextFormat().getPortionFormat().getFillFormat().setFillType(FillType.Solid);
labelFormat.getTextFormat().getPortionFormat().getFillFormat().getSolidFillColor().setColor(Color.WHITE);
}
presentation.save("SetDataLabelsPercentageSign_out.pptx", SaveFormat.Pptx);
} finally {
presentation.dispose();
}
Read the Actual Text of Data Labels
Use getActualLabelText to retrieve the text produced by a data label’s settings. This is useful when extracting labels for reports, searching presentation content, or validating generated charts. In the example below, the default data label format combines each category name, series name, and value. One point formats its value as a percentage, and another uses custom text from getTextFrameForOverriding.
import com.aspose.slides.*;
Presentation presentation = new Presentation();
try {
ISlide slide = presentation.getSlides().get_Item(0);
IChart chart = slide.getShapes().addChart(ChartType.ClusteredColumn, 20, 20, 500, 300);
chart.getChartData().getSeries().clear();
chart.getChartData().getCategories().clear();
IChartDataWorkbook workbook = chart.getChartData().getChartDataWorkbook();
IChartDataCell firstCategoryCell = workbook.getCell(0, 1, 0, "Q1");
chart.getChartData().getCategories().add(firstCategoryCell);
IChartDataCell secondCategoryCell = workbook.getCell(0, 2, 0, "Q2");
chart.getChartData().getCategories().add(secondCategoryCell);
IChartDataCell northSeriesCell = workbook.getCell(0, 0, 1, "North");
IChartSeries north = chart.getChartData().getSeries().add(northSeriesCell, chart.getType());
IChartDataCell northFirstValueCell = workbook.getCell(0, 1, 1, 0.25);
north.getDataPoints().addDataPointForBarSeries(northFirstValueCell);
IChartDataCell northSecondValueCell = workbook.getCell(0, 2, 1, 0.75);
north.getDataPoints().addDataPointForBarSeries(northSecondValueCell);
IChartDataCell southSeriesCell = workbook.getCell(0, 0, 2, "South");
IChartSeries south = chart.getChartData().getSeries().add(southSeriesCell, chart.getType());
IChartDataCell southFirstValueCell = workbook.getCell(0, 1, 2, 0.40);
south.getDataPoints().addDataPointForBarSeries(southFirstValueCell);
IChartDataCell southSecondValueCell = workbook.getCell(0, 2, 2, 0.60);
south.getDataPoints().addDataPointForBarSeries(southSecondValueCell);
for (IChartSeries series : chart.getChartData().getSeries()) {
IDataLabelFormat format = series.getLabels().getDefaultDataLabelFormat();
format.setShowCategoryName(true);
format.setShowSeriesName(true);
format.setShowValue(true);
}
north.getLabels().get_Item(1).getDataLabelFormat().setNumberFormatLinkedToSource(false);
north.getLabels().get_Item(1).getDataLabelFormat().setNumberFormat("0%");
south.getLabels().get_Item(0).getTextFrameForOverriding().setText("Reviewed");
for (IChartSeries series : chart.getChartData().getSeries()) {
for (IChartDataPoint point : series.getDataPoints()) {
IDataLabel label = point.getLabel();
if (!label.isVisible()) {
continue;
}
System.out.println("Value: " + point.getValue().getData() + "; label: " + label.getActualLabelText());
}
}
} finally {
presentation.dispose();
}
The number stored in a data point remains 0.75, even when its label shows 75% along with the category and series names. Custom text replaces the generated label text. getActualLabelText returns the resulting label string in either case. Check isVisible separately, as shown above, when you want to extract only visible labels.
Set Label Distance from an Axis
Use setLabelOffset to control the distance between category axis labels and the axis. The value is a percentage of the maximum font size of the axis labels. This example creates a clustered column chart and sets the horizontal axis label offset to 500. This setting affects category axis labels rather than labels attached to individual data points.
import com.aspose.slides.*;
Presentation presentation = new Presentation();
try {
ISlide slide = presentation.getSlides().get_Item(0);
IChart chart = slide.getShapes().addChart(ChartType.ClusteredColumn, 20, 20, 500, 300);
chart.getAxes().getHorizontalAxis().setLabelOffset(500);
presentation.save("SetCategoryAxisLabelDistance_out.pptx", SaveFormat.Pptx);
} finally {
presentation.dispose();
}
Adjust Label Location
On a pie chart, adjust data label positions to improve spacing and make room for leader lines.
This example displays the value of the first data point, places its label outside the slice, and adjusts its horizontal and vertical offsets using setX and setY. These offsets are relative to the chart width and height, respectively.
import com.aspose.slides.*;
Presentation presentation = new Presentation();
try {
ISlide slide = presentation.getSlides().get_Item(0);
IChart chart = slide.getShapes().addChart(ChartType.Pie, 50, 50, 200, 200);
IChartSeriesCollection series = chart.getChartData().getSeries();
IDataLabel label = series.get_Item(0).getLabels().get_Item(0);
label.getDataLabelFormat().setShowValue(true);
label.getDataLabelFormat().setPosition(LegendDataLabelPosition.OutsideEnd);
label.setX(0.71f);
label.setY(0.04f);
presentation.save("presentation.pptx", SaveFormat.Pptx);
} finally {
presentation.dispose();
}
FAQ
How can I prevent data labels from overlapping on dense charts?
Combine automatic label placement, leader lines, and reduced font size; if necessary, hide some fields (for example, the category) or show labels only for extreme values or key points.
How can I disable labels only for zero, negative, or empty values?
Filter data points before enabling labels and turn off display for values of 0, negative values, or missing values according to a defined rule.
How can I ensure a consistent label style when exporting to PDF/images?
Explicitly set the font family and size and verify that the font is available in the rendering environment to avoid fallback.