ChartDataLabelLocationMode

ChartDataLabelLocationMode enumeration

Specifies how the values ​​that specify the location of a data label - the Left and Top properties - are interpreted.

public enum ChartDataLabelLocationMode

Values

NameValueDescription
Offset0The location of a data label is specified by an offset from the position defined by its Position property.
Absolute1The location of a data label is specified using absolute coordinates, staring from the upper left corner of a chart.

Examples

Shows how to place data labels of doughnut chart outside doughnut.

Document doc = new Document();
DocumentBuilder builder = new DocumentBuilder(doc);

const int chartWidth = 432;
const int chartHeight = 252;
Shape shape = builder.InsertChart(ChartType.Doughnut, chartWidth, chartHeight);
Chart chart = shape.Chart;
ChartSeriesCollection seriesColl = chart.Series;
// Delete default generated series.
seriesColl.Clear();

// Hide the legend.
chart.Legend.Position = LegendPosition.None;

// Generate data.
const int dataLength = 20;
double totalValue = 0;
string[] categories = new string[dataLength];
double[] values = new double[dataLength];
for (int i = 0; i < dataLength; i++)
{
    categories[i] = string.Format("Category {0}", i);
    values[i] = dataLength - i;
    totalValue += values[i];
}

ChartSeries series = seriesColl.Add("Series 1", categories, values);
series.HasDataLabels = true;

ChartDataLabelCollection dataLabels = series.DataLabels;
dataLabels.ShowValue = true;
dataLabels.ShowLeaderLines = true;

// The Position property cannot be used for doughnut charts. Let's place data labels using the Left and Top
// properties around a circle outside of the chart doughnut.
// The origin is in the upper left corner of the chart.

const double titleAreaHeight = 25.5; // This can be calculated using title text and font.
const double doughnutCenterY = titleAreaHeight + (chartHeight - titleAreaHeight) / 2;
const double doughnutCenterX = chartWidth / 2d;
const double labelHeight = 16.5; // This can be calculated using label font.
const double oneCharLabelWidth = 12.75; // This can be calculated for each label using its text and font.
const double twoCharLabelWidth = 17.25; // This can be calculated for each label using its text and font.
const double yMargin = 0.75;
const double labelMargin = 1.5;
const double labelCircleRadius = chartHeight - doughnutCenterY - yMargin - labelHeight / 2;

// Because the data points start at the top, the X coordinates used in the Left and Top properties of
// the data labels point to the right and the Y coordinates point down, the starting angle is -PI/2.
double totalAngle = -System.Math.PI / 2;
ChartDataLabel previousLabel = null;

for (int i = 0; i < series.YValues.Count; i++)
{
    ChartDataLabel dataLabel = dataLabels[i];

    double value = series.YValues[i].DoubleValue;
    double labelWidth = (value < 10) ? oneCharLabelWidth : twoCharLabelWidth;
    double labelSegmentAngle = value / totalValue * 2 * System.Math.PI;
    double labelAngle = labelSegmentAngle / 2 + totalAngle;
    double labelCenterX = labelCircleRadius * System.Math.Cos(labelAngle) + doughnutCenterX;
    double labelCenterY = labelCircleRadius * System.Math.Sin(labelAngle) + doughnutCenterY;
    double labelLeft = labelCenterX - labelWidth / 2;
    double labelTop = labelCenterY - labelHeight / 2;

    // If the current data label overlaps other labels, move it horizontally.
    if ((previousLabel != null) &&
        (System.Math.Abs(previousLabel.Top - labelTop) < labelHeight) &&
        (System.Math.Abs(previousLabel.Left - labelLeft) < labelWidth))
    {
        // Move right on the top, left on the bottom.
        bool isOnTop = (totalAngle < 0) || (totalAngle >= System.Math.PI);
        labelLeft = previousLabel.Left + labelWidth * (isOnTop ? 1 : -1) + labelMargin;
    }

    dataLabel.Left = labelLeft;
    dataLabel.LeftMode = ChartDataLabelLocationMode.Absolute;
    dataLabel.Top = labelTop;
    dataLabel.TopMode = ChartDataLabelLocationMode.Absolute;

    totalAngle += labelSegmentAngle;
    previousLabel = dataLabel;
}

doc.Save(ArtifactsDir + "Charts.DoughnutChartLabelPosition.docx");

See Also

ChartDataLabelCollection Class ChartDataLabelPosition Enum