Manage Chart Data Labels in Presentations Using C++

What this page is about

Learn to add and format chart data labels in PowerPoint presentations using Aspose.Slides for C++ for more engaging slides.

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, control labels beyond the axis maximum, adjust category axis label spacing, and position pie chart labels.

Set Data Precision in Chart Data Labels

Use set_NumberFormatOfValues 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.

#include <DOM/Presentation.h>
#include <DOM/ISlide.h>
#include <DOM/IShapeCollection.h>
#include <DOM/IChart.h>
#include <DOM/Chart/ChartType.h>
#include <DOM/Chart/IChartData.h>
#include <DOM/Chart/IChartSeriesCollection.h>
#include <DOM/Chart/IChartSeries.h>
#include <DOM/Chart/IDataLabelCollection.h>
#include <DOM/Chart/IDataLabelFormat.h>
#include <Export/SaveFormat.h>
#include <system/smart_ptr.h>
#include <system/string.h>

using namespace Aspose::Slides;
using namespace Aspose::Slides::Charts;
using namespace Aspose::Slides::Export;
using namespace System;

auto presentation = MakeObject<Presentation>();
auto slide = presentation->get_Slide(0);

auto chart = slide->get_Shapes()->AddChart(ChartType::Line, 50, 50, 450, 300);
chart->set_HasDataTable(true);

auto series = chart->get_ChartData()->get_Series()->idx_get(0);
series->set_NumberFormatOfValues(u"#,##0.00");
series->get_Labels()->get_DefaultDataLabelFormat()->set_ShowValue(true);

presentation->Save(u"PrecisionOfDatalabels_out.pptx", SaveFormat::Pptx);

To format the numeric cells in a chart’s embedded workbook, see Set Custom Number Formats for Workbook Cells. That example also shows value labels following their source cell formats while preserving the stored numeric values.

Display Percentage 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 get_TextFrameForOverriding. 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.

#include <DOM/Presentation.h>
#include <DOM/ISlide.h>
#include <DOM/IShapeCollection.h>
#include <DOM/IChart.h>
#include <DOM/Chart/ChartType.h>
#include <DOM/Chart/IChartData.h>
#include <DOM/Chart/IChartCategoryCollection.h>
#include <DOM/Chart/IChartSeriesCollection.h>
#include <DOM/Chart/IChartSeries.h>
#include <DOM/Chart/IChartDataPointCollection.h>
#include <DOM/Chart/IChartDataPoint.h>
#include <DOM/Chart/IDoubleChartValue.h>
#include <DOM/Chart/IDataLabel.h>
#include <DOM/Chart/IDataLabelCollection.h>
#include <DOM/Chart/IDataLabelFormat.h>
#include <DOM/Portion.h>
#include <DOM/IPortionFormat.h>
#include <DOM/ITextFrame.h>
#include <DOM/IParagraph.h>
#include <DOM/IParagraphCollection.h>
#include <DOM/IPortionCollection.h>
#include <system/convert.h>
#include <vector>
#include <Export/SaveFormat.h>
#include <system/smart_ptr.h>
#include <system/string.h>

using namespace Aspose::Slides;
using namespace Aspose::Slides::Charts;
using namespace Aspose::Slides::Export;
using namespace System;

auto presentation = MakeObject<Presentation>();
auto slide = presentation->get_Slide(0);

auto chart = slide->get_Shapes()->AddChart(ChartType::StackedColumn, 20, 20, 400, 400);

auto categoryTotals = std::vector<double>(chart->get_ChartData()->get_Categories()->get_Count(), 0.0);
for (auto k = 0; k < chart->get_ChartData()->get_Categories()->get_Count(); k++)
{
    for (auto i = 0; i < chart->get_ChartData()->get_Series()->get_Count(); i++)
    {
        auto series = chart->get_ChartData()->get_Series()->idx_get(i);
        auto pointValue = Convert::ToDouble(series->get_DataPoint(k)->get_Value()->get_Data());
        categoryTotals[k] += pointValue;
    }
}

for (auto x = 0; x < chart->get_ChartData()->get_Series()->get_Count(); x++)
{
    auto series = chart->get_ChartData()->get_Series()->idx_get(x);
    series->get_Labels()->get_DefaultDataLabelFormat()->set_ShowLegendKey(false);

    for (auto j = 0; j < series->get_DataPoints()->get_Count(); j++)
    {
        auto label = series->get_DataPoint(j)->get_Label();
        if (categoryTotals[j] == 0)
        {
            continue;
        }

        auto pointValue = Convert::ToDouble(series->get_DataPoint(j)->get_Value()->get_Data());
        auto dataPointPercent = (pointValue / categoryTotals[j]) * 100;

        auto portion = MakeObject<Portion>();
        portion->set_Text(String::Format(u"{0:F2} %", dataPointPercent));
        portion->get_PortionFormat()->set_FontHeight(8.0f);

        label->get_TextFrameForOverriding()->set_Text(u"");

        auto paragraph = label->get_TextFrameForOverriding()->get_Paragraphs()->idx_get(0);
        paragraph->get_Portions()->Add(portion);

        label->get_DataLabelFormat()->set_ShowValue(true);
        label->get_DataLabelFormat()->set_ShowSeriesName(false);
        label->get_DataLabelFormat()->set_ShowPercentage(false);
        label->get_DataLabelFormat()->set_ShowLegendKey(false);
        label->get_DataLabelFormat()->set_ShowCategoryName(false);
        label->get_DataLabelFormat()->set_ShowBubbleSize(false);
    }
}

presentation->Save(u"DisplayPercentageAsLabels_out.pptx", SaveFormat::Pptx);

Set Percentage Sign with Chart Data Labels

When values are stored as fractions, use set_NumberFormat to display percentages. Pass false to set_IsNumberFormatLinkedToSource 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.

#include <DOM/Presentation.h>
#include <DOM/ISlide.h>
#include <DOM/IShapeCollection.h>
#include <DOM/IChart.h>
#include <DOM/Chart/ChartType.h>
#include <DOM/Chart/IAxesManager.h>
#include <DOM/Chart/IAxis.h>
#include <DOM/Chart/IChartData.h>
#include <DOM/Chart/IChartCategoryCollection.h>
#include <DOM/Chart/IChartDataWorkbook.h>
#include <DOM/Chart/IChartDataCell.h>
#include <DOM/Chart/IChartSeriesCollection.h>
#include <DOM/Chart/IChartSeries.h>
#include <DOM/Chart/IChartDataPointCollection.h>
#include <DOM/Chart/IFormat.h>
#include <DOM/Chart/IDataLabelCollection.h>
#include <DOM/Chart/IDataLabelFormat.h>
#include <DOM/Chart/IChartTextFormat.h>
#include <DOM/Chart/IChartPortionFormat.h>
#include <DOM/FillType.h>
#include <DOM/IFillFormat.h>
#include <DOM/IColorFormat.h>
#include <drawing/color.h>
#include <system/object_ext.h>
#include <Export/SaveFormat.h>
#include <system/smart_ptr.h>
#include <system/string.h>

using namespace Aspose::Slides;
using namespace Aspose::Slides::Charts;
using namespace Aspose::Slides::Export;
using namespace System;
using namespace System::Drawing;

auto presentation = MakeObject<Presentation>();
auto slide = presentation->get_Slide(0);

auto chart = slide->get_Shapes()->AddChart(ChartType::PercentsStackedColumn, 20, 20, 500, 400);

chart->get_Axes()->get_VerticalAxis()->set_IsNumberFormatLinkedToSource(false);
chart->get_Axes()->get_VerticalAxis()->set_NumberFormat(u"0.00%");

chart->get_ChartData()->get_Series()->Clear();
chart->get_ChartData()->get_Categories()->Clear();

auto workbook = chart->get_ChartData()->get_ChartDataWorkbook();
auto worksheetIndex = 0;
for (auto i = 0; i < 4; i++)
{
    auto categoryCell = workbook->GetCell(worksheetIndex, i + 1, 0, ObjectExt::Box(String::Format(u"Category {0}", i + 1)));
    chart->get_ChartData()->get_Categories()->Add(categoryCell);
}

String seriesNames[] = { u"Reds", u"Blues" };
Color seriesColors[] = { Color::get_Red(), Color::get_Blue() };
double values[2][4] = { { 0.30, 0.50, 0.80, 0.65 }, { 0.70, 0.50, 0.20, 0.35 } };

for (auto i = 0; i < 2; i++)
{
    auto seriesCell = workbook->GetCell(worksheetIndex, 0, i + 1, ObjectExt::Box(seriesNames[i]));
    auto series = chart->get_ChartData()->get_Series()->Add(seriesCell, chart->get_Type());
    for (auto j = 0; j < 4; j++)
    {
        auto valueCell = workbook->GetCell(worksheetIndex, j + 1, i + 1, ObjectExt::Box(values[i][j]));
        series->get_DataPoints()->AddDataPointForBarSeries(valueCell);
    }

    series->get_Format()->get_Fill()->set_FillType(FillType::Solid);
    series->get_Format()->get_Fill()->get_SolidFillColor()->set_Color(seriesColors[i]);

    auto labelFormat = series->get_Labels()->get_DefaultDataLabelFormat();
    labelFormat->set_ShowValue(true);
    labelFormat->set_IsNumberFormatLinkedToSource(false);
    labelFormat->set_NumberFormat(u"0.0%");
    labelFormat->get_TextFormat()->get_PortionFormat()->set_FontHeight(10);
    labelFormat->get_TextFormat()->get_PortionFormat()->get_FillFormat()->set_FillType(FillType::Solid);
    labelFormat->get_TextFormat()->get_PortionFormat()->get_FillFormat()->get_SolidFillColor()->set_Color(Color::get_White());
}

presentation->Save(u"SetDataLabelsPercentageSign_out.pptx", SaveFormat::Pptx);

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 get_TextFrameForOverriding.

#include <DOM/Presentation.h>
#include <DOM/ISlide.h>
#include <DOM/IShapeCollection.h>
#include <DOM/IChart.h>
#include <DOM/Chart/ChartType.h>
#include <DOM/Chart/IChartData.h>
#include <DOM/Chart/IChartCategoryCollection.h>
#include <DOM/Chart/IChartDataWorkbook.h>
#include <DOM/Chart/IChartDataCell.h>
#include <DOM/Chart/IChartSeriesCollection.h>
#include <DOM/Chart/IChartSeries.h>
#include <DOM/Chart/IChartDataPointCollection.h>
#include <DOM/Chart/IChartDataPoint.h>
#include <DOM/Chart/IDoubleChartValue.h>
#include <DOM/Chart/IDataLabel.h>
#include <DOM/Chart/IDataLabelCollection.h>
#include <DOM/Chart/IDataLabelFormat.h>
#include <DOM/ITextFrame.h>
#include <system/console.h>
#include <system/object_ext.h>
#include <system/smart_ptr.h>
#include <system/string.h>

using namespace Aspose::Slides;
using namespace Aspose::Slides::Charts;
using namespace System;

auto presentation = MakeObject<Presentation>();
auto slide = presentation->get_Slide(0);

auto chart = slide->get_Shapes()->AddChart(ChartType::ClusteredColumn, 20, 20, 500, 300);

chart->get_ChartData()->get_Series()->Clear();
chart->get_ChartData()->get_Categories()->Clear();

auto workbook = chart->get_ChartData()->get_ChartDataWorkbook();
auto firstCategoryCell = workbook->GetCell(0, 1, 0, ObjectExt::Box<String>(u"Q1"));
chart->get_ChartData()->get_Categories()->Add(firstCategoryCell);
auto secondCategoryCell = workbook->GetCell(0, 2, 0, ObjectExt::Box<String>(u"Q2"));
chart->get_ChartData()->get_Categories()->Add(secondCategoryCell);

auto northSeriesCell = workbook->GetCell(0, 0, 1, ObjectExt::Box<String>(u"North"));
auto north = chart->get_ChartData()->get_Series()->Add(northSeriesCell, chart->get_Type());
auto northFirstValueCell = workbook->GetCell(0, 1, 1, ObjectExt::Box(0.25));
north->get_DataPoints()->AddDataPointForBarSeries(northFirstValueCell);
auto northSecondValueCell = workbook->GetCell(0, 2, 1, ObjectExt::Box(0.75));
north->get_DataPoints()->AddDataPointForBarSeries(northSecondValueCell);

auto southSeriesCell = workbook->GetCell(0, 0, 2, ObjectExt::Box<String>(u"South"));
auto south = chart->get_ChartData()->get_Series()->Add(southSeriesCell, chart->get_Type());
auto southFirstValueCell = workbook->GetCell(0, 1, 2, ObjectExt::Box(0.40));
south->get_DataPoints()->AddDataPointForBarSeries(southFirstValueCell);
auto southSecondValueCell = workbook->GetCell(0, 2, 2, ObjectExt::Box(0.60));
south->get_DataPoints()->AddDataPointForBarSeries(southSecondValueCell);

for (auto i = 0; i < chart->get_ChartData()->get_Series()->get_Count(); i++)
{
    auto series = chart->get_ChartData()->get_Series()->idx_get(i);
    auto format = series->get_Labels()->get_DefaultDataLabelFormat();
    format->set_ShowCategoryName(true);
    format->set_ShowSeriesName(true);
    format->set_ShowValue(true);
}

north->get_Label(1)->get_DataLabelFormat()->set_IsNumberFormatLinkedToSource(false);
north->get_Label(1)->get_DataLabelFormat()->set_NumberFormat(u"0%");
south->get_Label(0)->get_TextFrameForOverriding()->set_Text(u"Reviewed");

for (auto i = 0; i < chart->get_ChartData()->get_Series()->get_Count(); i++)
{
    auto series = chart->get_ChartData()->get_Series()->idx_get(i);
    for (auto j = 0; j < series->get_DataPoints()->get_Count(); j++)
    {
        auto point = series->get_DataPoint(j);
        auto label = point->get_Label();
        if (!label->get_IsVisible())
        {
            continue;
        }

        Console::WriteLine(String::Format(u"Value: {0}; label: {1}", point->get_Value()->get_Data(), label->GetActualLabelText()));
    }
}

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 get_IsVisible separately, as shown above, when you want to extract only visible labels.

Control Data Labels Beyond the Axis Maximum

When you limit an axis range manually, some data points may exceed its maximum. Use set_ShowDataLabelsOverMaximum to control whether their data labels are shown. This setting changes label visibility; it does not change the axis range or the underlying data values.

The example below creates a 2D clustered column chart with values of 60 and 120. It sets set_IsAutomaticMaxValue to false and set_MaxValue to 100 on the vertical axis. The first slide allows labels beyond the maximum; a copy of that slide disables them. Both slides are saved in DataLabelsOverMaximum.pptx.

Enable value labels with set_ShowValue. The chart-level setting does not enable value display by itself or override an individual label’s disabled value display. This example enables values for the entire series and uses set_Position to place labels at the outside end of each column.

#include <DOM/Presentation.h>
#include <DOM/ISlide.h>
#include <DOM/ISlideCollection.h>
#include <DOM/IShapeCollection.h>
#include <DOM/IChart.h>
#include <DOM/Chart/ChartType.h>
#include <DOM/Chart/IAxesManager.h>
#include <DOM/Chart/IAxis.h>
#include <DOM/Chart/IChartData.h>
#include <DOM/Chart/IChartCategoryCollection.h>
#include <DOM/Chart/IChartDataWorkbook.h>
#include <DOM/Chart/IChartDataCell.h>
#include <DOM/Chart/IChartSeriesCollection.h>
#include <DOM/Chart/IChartSeries.h>
#include <DOM/Chart/IChartDataPointCollection.h>
#include <DOM/Chart/IDataLabelCollection.h>
#include <DOM/Chart/IDataLabelFormat.h>
#include <DOM/Chart/LegendDataLabelPosition.h>
#include <Export/SaveFormat.h>
#include <system/object_ext.h>
#include <system/smart_ptr.h>
#include <system/string.h>

using namespace Aspose::Slides;
using namespace Aspose::Slides::Charts;
using namespace Aspose::Slides::Export;
using namespace System;

auto presentation = MakeObject<Presentation>();
auto slide = presentation->get_Slide(0);

auto chart = slide->get_Shapes()->AddChart(ChartType::ClusteredColumn, 50, 50, 600, 400);
chart->set_HasLegend(false);

chart->get_ChartData()->get_Series()->Clear();
chart->get_ChartData()->get_Categories()->Clear();

auto workbook = chart->get_ChartData()->get_ChartDataWorkbook();

auto firstCategory = workbook->GetCell(0, 1, 0, ObjectExt::Box<String>(u"Within range"));
auto secondCategory = workbook->GetCell(0, 2, 0, ObjectExt::Box<String>(u"Above maximum"));

chart->get_ChartData()->get_Categories()->Add(firstCategory);
chart->get_ChartData()->get_Categories()->Add(secondCategory);

auto seriesName = workbook->GetCell(0, 0, 1, ObjectExt::Box<String>(u"Values"));
auto series = chart->get_ChartData()->get_Series()->Add(seriesName, chart->get_Type());

auto firstValue = workbook->GetCell(0, 1, 1, ObjectExt::Box(60));
auto secondValue = workbook->GetCell(0, 2, 1, ObjectExt::Box(120));

series->get_DataPoints()->AddDataPointForBarSeries(firstValue);
series->get_DataPoints()->AddDataPointForBarSeries(secondValue);

series->get_Labels()->get_DefaultDataLabelFormat()->set_ShowValue(true);
series->get_Labels()->get_DefaultDataLabelFormat()->set_Position(LegendDataLabelPosition::OutsideEnd);

chart->get_Axes()->get_VerticalAxis()->set_IsAutomaticMaxValue(false);
chart->get_Axes()->get_VerticalAxis()->set_MaxValue(100);
chart->set_ShowDataLabelsOverMaximum(true);

auto secondSlide = presentation->get_Slides()->AddClone(slide);
auto secondChart = ExplicitCast<IChart>(secondSlide->get_Shape(0));
secondChart->set_ShowDataLabelsOverMaximum(false);

presentation->Save(u"DataLabelsOverMaximum.pptx", SaveFormat::Pptx);

The following images show the saved slides rendered by Microsoft PowerPoint. With true, the label 120 is visible at the upper boundary; with false, it is hidden. The label 60 remains visible, the axis maximum stays at 100, and the second data point remains 120 in both cases.

ShowDataLabelsOverMaximum = true	ShowDataLabelsOverMaximum = false

Chart Type

This example uses a 2D column chart with a value axis. Charts without a value axis, such as pie and doughnut charts, do not have an axis maximum to limit in this way.

Set Label Distance from an Axis

Use set_LabelOffset 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.

#include <DOM/Presentation.h>
#include <DOM/ISlide.h>
#include <DOM/IShapeCollection.h>
#include <DOM/IChart.h>
#include <DOM/Chart/ChartType.h>
#include <DOM/Chart/IAxesManager.h>
#include <DOM/Chart/IAxis.h>
#include <Export/SaveFormat.h>
#include <system/smart_ptr.h>
#include <system/string.h>

using namespace Aspose::Slides;
using namespace Aspose::Slides::Charts;
using namespace Aspose::Slides::Export;
using namespace System;

auto presentation = MakeObject<Presentation>();
auto slide = presentation->get_Slide(0);

auto chart = slide->get_Shapes()->AddChart(ChartType::ClusteredColumn, 20, 20, 500, 300);
chart->get_Axes()->get_HorizontalAxis()->set_LabelOffset(500);

presentation->Save(u"SetCategoryAxisLabelDistance_out.pptx", SaveFormat::Pptx);

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 uses set_X and set_Y to adjust its offsets. These offsets are relative to the chart width and height, respectively.

#include <DOM/Presentation.h>
#include <DOM/ISlide.h>
#include <DOM/IShapeCollection.h>
#include <DOM/IChart.h>
#include <DOM/Chart/ChartType.h>
#include <DOM/Chart/IChartData.h>
#include <DOM/Chart/IChartSeriesCollection.h>
#include <DOM/Chart/IChartSeries.h>
#include <DOM/Chart/IDataLabel.h>
#include <DOM/Chart/IDataLabelFormat.h>
#include <DOM/Chart/LegendDataLabelPosition.h>
#include <Export/SaveFormat.h>
#include <system/smart_ptr.h>
#include <system/string.h>

using namespace Aspose::Slides;
using namespace Aspose::Slides::Charts;
using namespace Aspose::Slides::Export;
using namespace System;

auto presentation = MakeObject<Presentation>();
auto slide = presentation->get_Slide(0);

auto chart = slide->get_Shapes()->AddChart(ChartType::Pie, 50, 50, 200, 200);
auto series = chart->get_ChartData()->get_Series();

auto label = series->idx_get(0)->get_Label(0);
label->get_DataLabelFormat()->set_ShowValue(true);
label->get_DataLabelFormat()->set_Position(LegendDataLabelPosition::OutsideEnd);
label->set_X(0.71f);
label->set_Y(0.04f);

presentation->Save(u"presentation.pptx", SaveFormat::Pptx);

Format Leader Lines

When pie chart labels sit outside their slices, leader lines help readers match each value to the correct slice. A contrasting color and a slightly thicker line can make these connections easier to follow, while transparency and a dashed style keep the lines visually unobtrusive.

Use get_LeaderLinesFormat to format leader lines at the series' data label collection level. The settings in series->get_Labels()->get_LeaderLinesFormat()->get_Line() apply to the collection, rather than to an individual label.

This example creates a pie chart with default data, displays values outside the slices, and enables leader lines with set_ShowLeaderLines. It moves two labels farther from their slices using set_X and set_Y offsets, expressed as fractions of the chart width and height. No input presentation is required.

The fill format returned by get_FillFormat is used to set a solid blue color with an alpha value of 191 out of 255, giving approximately 25% transparency. set_Width sets the thickness to 2 points, and set_DashStyle makes the line dashed.

#include <DOM/Presentation.h>
#include <DOM/ISlide.h>
#include <DOM/IShapeCollection.h>
#include <DOM/IChart.h>
#include <DOM/Chart/ChartType.h>
#include <DOM/Chart/IChartData.h>
#include <DOM/Chart/IChartSeriesCollection.h>
#include <DOM/Chart/IChartSeries.h>
#include <DOM/Chart/IDataLabel.h>
#include <DOM/Chart/IDataLabelCollection.h>
#include <DOM/Chart/IDataLabelFormat.h>
#include <DOM/Chart/IChartLinesFormat.h>
#include <DOM/Chart/LegendDataLabelPosition.h>
#include <DOM/ILineFormat.h>
#include <DOM/ILineFillFormat.h>
#include <DOM/IColorFormat.h>
#include <DOM/FillType.h>
#include <DOM/LineDashStyle.h>
#include <Export/SaveFormat.h>
#include <drawing/color.h>
#include <system/smart_ptr.h>
#include <system/string.h>

using namespace Aspose::Slides;
using namespace Aspose::Slides::Charts;
using namespace Aspose::Slides::Export;
using namespace System;
using namespace System::Drawing;

auto presentation = MakeObject<Presentation>();
auto slide = presentation->get_Slide(0);

auto chart = slide->get_Shapes()->AddChart(ChartType::Pie, 80, 50, 560, 400);
chart->set_HasLegend(false);

auto series = chart->get_ChartData()->get_Series()->idx_get(0);

auto labelFormat = series->get_Labels()->get_DefaultDataLabelFormat();
labelFormat->set_ShowValue(true);
labelFormat->set_Position(LegendDataLabelPosition::OutsideEnd);
labelFormat->set_ShowLeaderLines(true);

// Move two labels farther away from their slices.
series->get_Label(0)->set_X(0.10f);
series->get_Label(0)->set_Y(-0.05f);
series->get_Label(1)->set_X(-0.10f);
series->get_Label(1)->set_Y(0.05f);

auto line = series->get_Labels()->get_LeaderLinesFormat()->get_Line();
line->get_FillFormat()->set_FillType(FillType::Solid);
line->get_FillFormat()->get_SolidFillColor()->set_Color(Color::FromArgb(191, 30, 90, 160));
line->set_Width(2);
line->set_DashStyle(LineDashStyle::Dash);

presentation->Save(u"FormattedLeaderLines.pptx", SaveFormat::Pptx);

Enabling leader lines does not guarantee that a line will appear for every label. Visibility depends on label placement and the chart’s layout behavior. In this example, the two displaced labels have visible leader lines; the labels that remain close to their slices do not need them.

The following image shows the saved FormattedLeaderLines.pptx rendered with Aspose.Slides:

Add Multiple Rows of Data Labels Above a Column Chart

This example creates a column chart with two rows of data labels above the plot area. Series A displays the visible columns, while Series B and Series C provide the additional labels. Their columns are hidden by removing the fill and outline. The set_Overlap method aligns all three series with the same category centers.

The get_PlotArea settings reserve space for the label rows. After ValidateChartLayout calculates the default positions, set_X and set_Y preserve the horizontal alignment and apply vertical offsets to arrange the labels in two rows. The numbers remain data labels linked to the series values; only the row headings are separate text shapes.

#include <DOM/Presentation.h>
#include <DOM/ISlide.h>
#include <DOM/IShapeCollection.h>
#include <DOM/IChart.h>
#include <DOM/Chart/ChartType.h>
#include <DOM/Chart/IChartData.h>
#include <DOM/Chart/IChartCategoryCollection.h>
#include <DOM/Chart/IChartDataWorkbook.h>
#include <DOM/Chart/IChartDataCell.h>
#include <DOM/Chart/IChartSeriesCollection.h>
#include <DOM/Chart/IChartSeries.h>
#include <DOM/Chart/IChartDataPointCollection.h>
#include <DOM/Chart/IChartDataPoint.h>
#include <DOM/Chart/IChartSeriesGroup.h>
#include <DOM/Chart/IFormat.h>
#include <DOM/Chart/IDataLabelCollection.h>
#include <DOM/Chart/IDataLabelFormat.h>
#include <DOM/Chart/IDataLabel.h>
#include <DOM/Chart/IChartTextFormat.h>
#include <DOM/Chart/IChartPortionFormat.h>
#include <DOM/Chart/LegendDataLabelPosition.h>
#include <DOM/Chart/IAxesManager.h>
#include <DOM/Chart/IAxis.h>
#include <DOM/Chart/IChartPlotArea.h>
#include <DOM/Chart/LayoutTargetType.h>
#include <DOM/FillType.h>
#include <DOM/IFillFormat.h>
#include <DOM/ILineFormat.h>
#include <DOM/IColorFormat.h>
#include <DOM/ShapeType.h>
#include <DOM/IAutoShape.h>
#include <DOM/ITextFrame.h>
#include <DOM/ITextFrameFormat.h>
#include <DOM/IParagraphCollection.h>
#include <DOM/IParagraph.h>
#include <DOM/IPortionCollection.h>
#include <DOM/IPortion.h>
#include <DOM/IPortionFormat.h>
#include <Export/SaveFormat.h>
#include <drawing/color.h>
#include <system/object_ext.h>
#include <system/smart_ptr.h>
#include <system/string.h>

using namespace Aspose::Slides;
using namespace Aspose::Slides::Charts;
using namespace Aspose::Slides::Export;
using namespace System;
using namespace System::Drawing;

auto presentation = MakeObject<Presentation>();
auto slide = presentation->get_Slide(0);

auto chart = slide->get_Shapes()->AddChart(ChartType::ClusteredColumn, 40, 40, 640, 200);
chart->set_HasTitle(false);
chart->set_HasLegend(false);
chart->get_TextFormat()->get_PortionFormat()->set_FontHeight(12);

chart->get_ChartData()->get_Series()->Clear();
chart->get_ChartData()->get_Categories()->Clear();

auto workbook = chart->get_ChartData()->get_ChartDataWorkbook();
workbook->Clear(0);

String categories[] = { u"North", u"South", u"East", u"West" };
String seriesNames[] = { u"Series A", u"Series B", u"Series C" };
double seriesValues[3][4] = {
    { 35, 42, 28, 47 },
    { 22, 31, 19, 26 },
    { 12, 16, 14, 18 }
};

for (auto categoryIndex = 0; categoryIndex < 4; categoryIndex++)
{
    auto categoryCell = workbook->GetCell(0, categoryIndex + 1, 0, ObjectExt::Box(categories[categoryIndex]));
    chart->get_ChartData()->get_Categories()->Add(categoryCell);
}

for (auto seriesIndex = 0; seriesIndex < 3; seriesIndex++)
{
    auto seriesCell = workbook->GetCell(0, 0, seriesIndex + 1, ObjectExt::Box(seriesNames[seriesIndex]));
    auto series = chart->get_ChartData()->get_Series()->Add(seriesCell, ChartType::ClusteredColumn);

    for (auto categoryIndex = 0; categoryIndex < 4; categoryIndex++)
    {
        auto valueCell = workbook->GetCell(0, categoryIndex + 1, seriesIndex + 1, ObjectExt::Box(seriesValues[seriesIndex][categoryIndex]));
        series->get_DataPoints()->AddDataPointForBarSeries(valueCell);
    }

    if (seriesIndex > 0)
    {
        // Hide the columns of B and C, but keep their data labels.
        series->get_Format()->get_Fill()->set_FillType(FillType::NoFill);
        series->get_Format()->get_Line()->get_FillFormat()->set_FillType(FillType::NoFill);
        auto labelFormat = series->get_Labels()->get_DefaultDataLabelFormat();
        labelFormat->set_ShowValue(true);
        labelFormat->get_TextFormat()->get_PortionFormat()->set_FontHeight(12);
        auto labelFill = labelFormat->get_TextFormat()->get_PortionFormat()->get_FillFormat();
        labelFill->set_FillType(FillType::Solid);
        labelFill->get_SolidFillColor()->set_Color(Color::get_Black());
        labelFormat->set_Position(LegendDataLabelPosition::InsideBase);
    }
}

// Align all three series with the same category centers.
chart->get_ChartData()->get_Series()->idx_get(0)->get_ParentSeriesGroup()->set_Overlap(100);

// Use fewer gridlines for this compact example.
chart->get_Axes()->get_VerticalAxis()->set_IsAutomaticMajorUnit(false);
chart->get_Axes()->get_VerticalAxis()->set_MajorUnit(10);

// Reserve space above the plot for two rows of data labels.
chart->get_PlotArea()->set_LayoutTargetType(LayoutTargetType::Inner);
chart->get_PlotArea()->set_X(0.15f);
chart->get_PlotArea()->set_Y(0.32f);
chart->get_PlotArea()->set_Width(0.80f);
chart->get_PlotArea()->set_Height(0.48f);
chart->ValidateChartLayout();

for (auto seriesIndex = 1; seriesIndex < 3; seriesIndex++)
{
    auto series = chart->get_ChartData()->get_Series()->idx_get(seriesIndex);
    auto rowTop = seriesIndex == 1 ? 0.15f : 0.03f;

    for (auto categoryIndex = 0; categoryIndex < 4; categoryIndex++)
    {
        auto dataLabel = series->get_DataPoint(categoryIndex)->get_Label();
        // Keep the default horizontal position. Y is an offset from
        // the default label position, expressed as a chart-height fraction.
        dataLabel->set_X(0);
        dataLabel->set_Y(rowTop - dataLabel->get_ActualY() / chart->get_Height());
    }

    // Only the row heading is a separate text shape.
    auto rowHeading = slide->get_Shapes()->AddAutoShape(ShapeType::Rectangle, chart->get_X(), chart->get_Y() + rowTop * chart->get_Height(), 85, 18);
    rowHeading->get_FillFormat()->set_FillType(FillType::NoFill);
    rowHeading->get_LineFormat()->get_FillFormat()->set_FillType(FillType::NoFill);
    rowHeading->AddTextFrame(seriesNames[seriesIndex]);
    rowHeading->get_TextFrame()->get_TextFrameFormat()->set_MarginTop(0);
    rowHeading->get_TextFrame()->get_TextFrameFormat()->set_MarginBottom(0);
    auto headingFormat = rowHeading->get_TextFrame()->get_Paragraphs()->idx_get(0)->get_Portions()->idx_get(0)->get_PortionFormat();
    headingFormat->set_FontHeight(12);
    headingFormat->get_FillFormat()->set_FillType(FillType::Solid);
    headingFormat->get_FillFormat()->get_SolidFillColor()->set_Color(Color::get_Black());
}

presentation->Save(u"multiple-rows-of-labels.pptx", SaveFormat::Pptx);

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.