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HeatmapControl Class

Displays a customizable and interactive heatmap chart.

Namespace: DevExpress.XtraCharts.Heatmap

Assembly: DevExpress.XtraCharts.v21.2.UI.dll

Declaration

public class HeatmapControl :
    Control,
    IChartContainer,
    IChartRenderProvider,
    IHeatmapInteractionContainer,
    IToolTipControlClient,
    ICursorHolder,
    ISupportLookAndFeel,
    IPrintable,
    IBasePrintable

Remarks

A heatmap is a data analysis tool that uses colors and color intensity to visualize a change in magnitude. Each heatmap cell is defined by three values: X-argument, Y-argument, and Value (Color Value). The arguments are displayed along corresponding axes. The value is used to determine the cell color.

The following image depicts the main elements of a heatmap:

Heatmap elements

Demos

The Heatmap Control ships with a set of demo applications that you can explore in the DevExpress Demo Center:

Run Demo: Color Providers

Run Demo: Large Data

Run Demo: Labels

Run Demo: Tooltip

Add a Heatmap Control to the Project

Drag and drop the HeatmapControl component from the Visual Studio Toolbox to the form to add a heatmap chart control to the project.

HeatmapControl in Toolbox

This adds references to the following assemblies in the project:

  • DevExpress.Charts.v21.2.Core.dll
  • DevExpress.Data.Desktop.v21.2.dll
  • DevExpress.Data.v21.2.dll
  • DevExpress.Printing.v21.2.Core.dll
  • DevExpress.XtraPrinting.v21.2.dll
  • DevExpress.Utils.v21.2.dll
  • DevExpress.Utils.v21.2.UI.dll
  • DevExpress.XtraBars.v21.2.dll
  • DevExpress.XtraCharts.v21.2.dll
  • DevExpress.XtraCharts.v21.2.UI.dll
  • DevExpress.XtraCharts.v21.2.Wizard.dll
  • DevExpress.XtraEditors.v21.2.dll

Load Data to a Heatmap

The Heatmap Control uses data adapters to load data. Heatmap data adapters are derived from the HeatmapDataAdapterBase class. Use the Heatmap Control’s DataAdapter property to assign an adapter to a heatmap. The following adapters are available:

  • HeatmapDataSourceAdapter – Allows you to bind the Heatmap Control to a data source.
  • HeatmapMatrixAdapter – Allows you to use collections of values to specify x-arguments and y-arguments, and pass a matrix of numeric values to define heatmap cell values.

Paint a Heatmap

The Heatmap Control ships with multiple color providers that implement different coloring algorithms:

To assign a color provider object to a heatmap, use the HeatmapControl.ColorProvider property.

Add Titles

You can add multiple titles to a heatmap. To do this, add HeatmapTitle objects to the Heatmap Control’s Titles collection.

Configure Cell Labels

Use the HeatmapControl.Label property to access heatmap cell label settings. Enable the HeatmapLabel.Visible property to display labels. Specify the HeatmapLabel.Pattern property to format labels.

Configure Axes

Use the AxisX and AxisY properties to access heatmap axis settings. The Heatmap Control includes the following axis options:

  • Alignment - Specifies the title position on the heatmap chart.
  • Color - Specifies the color of the axis and its tickmarks.
  • Label - Allows you to access axis label settings, such as display format, position, or color.
  • CustomLabels - Allows you to replace default axis labels with custom labels.
  • GridSpacing - Defines the frequency of axis tickmarks and labels.
  • Reverse - Allows you to display axis labels and corresponding rows (columns) in reversed order.
  • Thickness - Defines axis thickness.
  • Tickmarks - Allows you to access tickmark settings.
  • Title - Specifies axis title options.
  • Visibility - Specifies whether an axis is visible.

Refer to the HeatmapAxis class description to learn more about axis customization.

Customize Legend

You can display a single legend for a heatmap. Legend item content depends on the color provider assigned to the heatmap. For example, the Range Color Provider generates legend items that show value ranges. To format legend item content, use the color provider’s LegendItemPattern property. Use the Legend property to access legend options, such as position, title, and so on.

Obtain Hit Information about Heatmap Elements

Call the CalcHitInfo method to check what heatmap element is located in the test point. This method returns a HeatmapHitInfo object that contains information about the test point and heatmap element.

Zoom and Scroll Heatmap

Enable the following properties to allow users to scroll and zoom a heatmap:

You can use the HeatmapControl.Scroll, HeatmapControl.ZoomIn and HeatmapControl.ZoomOut methods to scroll and zoom a heatmap programmatically.

After a heatmap is zoomed, you can call the Heatmap Control’s ResetZoom() method to reset the heatmap to the initial state (when the heatmap is not zoomed).

Enable and Customize Tooltips

Set the HeatmapControl.ToolTipEnabled property to true to display tooltips when a user hovers over a heatmap cell.

Use the HeatmapControl.ToolTipController property to access tooltip settings.

Specify the HeatmapControl.ToolTipTextPattern property to format tooltip text. For advanced tooltip content customization, handle the HeatmapControl.CustomizeHeatmapToolTip event.

Highlight Heatmap Cells

A user can hover over a heatmap cell with the mouse cursor to highlight this cell. Specify the HeatmapControl.HighlightMode property to select an appropriate highlight mode.

If you want to perform custom actions when a user highlights a heatmap cell, handle the HeatmapControl.HighlightedItemChanged event.

Use one of the methods below to print the Heatmap control:

The following methods allow you to export the Heatmap control to different formats:

Examples

How to Create a Heatmap Based on a Matrix of Numeric Values

This example shows how to use arrays of string and numeric values to create a heatmap.

A heatmap that uses a Matrix Adapter

Follow the steps below to create a heatmap:

  • Add the HeatmapControl to the Form.
  • Create a HeatmapMatrixAdapter object and assign it to the HeatmapControl.DataAdapter property.
  • Use the adapter’s XArguments and YArguments properties to populate the heatmap with x- and y-arguments that are displayed along x- and y-axes.
  • Assign a two-dimensional array of double values to the adapter’s Values property.
  • Create a HeatmapRangeColorProvider object and assign it to the heatmap’s ColorProvider property. The HeatmapRangeColorProvider paints cells based on a value range to which the cell value belongs.
  • Add a HeatmapTitle to the heatmap’s Titles collection. Specify the title’s Text property.
  • Use the heatmap’s Label property to configure cell label options. This example shows how to configure label text format.

View Example

using DevExpress.XtraCharts;
using DevExpress.XtraCharts.Heatmap;
using System.Drawing;
using System.Windows.Forms;

namespace HeatmapMatrixData {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();

            HeatmapMatrixAdapter dataAdapter = new HeatmapMatrixAdapter();
            dataAdapter.XArguments = new string[] { "North", "South", "West", "East", "Central" };
            dataAdapter.YArguments = new string[] { "Components", "Clothing", "Bikes", "Accessories" };
            dataAdapter.Values = new double[,] {
                { 21.3, 50.1, 63.2, 64.4, 33.4 },
                { 32.3, 54.4, 81.3, 53.4, 54.9 },
                { 60.3, 49.1, 42.6, 48.4, 65.4 },
                { 45.3, 54.7, 70.3, 66.4, 56.6 }
            };
            heatmap.DataAdapter = dataAdapter;

            Palette palette = new Palette("Custom") {
                Color.White,
                Color.SkyBlue,
                Color.DarkBlue
            };

            HeatmapRangeColorProvider colorProvider = new HeatmapRangeColorProvider() {
                Palette = palette,
                ApproximateColors = true
            };
            colorProvider.RangeStops.Add(new HeatmapRangeStop(0, HeatmapRangeStopType.Percentage));
            colorProvider.RangeStops.Add(new HeatmapRangeStop(20, HeatmapRangeStopType.Absolute));
            colorProvider.RangeStops.Add(new HeatmapRangeStop(40, HeatmapRangeStopType.Absolute));
            colorProvider.RangeStops.Add(new HeatmapRangeStop(60, HeatmapRangeStopType.Absolute));
            colorProvider.RangeStops.Add(new HeatmapRangeStop(90, HeatmapRangeStopType.Absolute));
            colorProvider.RangeStops.Add(new HeatmapRangeStop(1, HeatmapRangeStopType.Percentage));

            heatmap.ColorProvider = colorProvider;

            heatmap.Titles.Add(new HeatmapTitle { Text = "Sales by Categories" });

            heatmap.Label.Visible = true;
            heatmap.Label.Pattern = "{V}";
        }
    }
}

How to Bind a Heatmap to a Data Source (XML File)

The following example shows how to create a heatmap and bind it to a data source. In this example, the heatmap obtains data from an XML file.

A heatmap that uses a Data Source Adapter to load data.

View Example

using DevExpress.XtraCharts;
using DevExpress.XtraCharts.Heatmap;
using System.Data;
using System.Drawing;
using System.IO;
using System.Windows.Forms;

namespace BindHeatmapToDataSource {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
            DataTable data = CreateDataSet("BalanceOfTrade.xml");

            heatmap.DataAdapter = new HeatmapDataSourceAdapter() {
                XArgumentDataMember = "Country",
                YArgumentDataMember = "Product",
                ColorDataMember = "Value",
                DataSource = data
            };

            Palette palette = new Palette("Custom") { Color.Red, Color.White, Color.Green };

            HeatmapRangeColorProvider colorProvider = new HeatmapRangeColorProvider() {
                Palette = palette,
                ApproximateColors = true,
                LegendItemPattern = "{V1} .. {V2}"
            };

            heatmap.ColorProvider = colorProvider;

            colorProvider.RangeStops.Add(new HeatmapRangeStop(0, HeatmapRangeStopType.Percentage));
            colorProvider.RangeStops.Add(new HeatmapRangeStop(-10));
            colorProvider.RangeStops.Add(new HeatmapRangeStop(-2.5));
            colorProvider.RangeStops.Add(new HeatmapRangeStop(0));
            colorProvider.RangeStops.Add(new HeatmapRangeStop(2.5));
            colorProvider.RangeStops.Add(new HeatmapRangeStop(10));
            colorProvider.RangeStops.Add(new HeatmapRangeStop(1, HeatmapRangeStopType.Percentage));


            heatmap.Titles.Add(new HeatmapTitle { Text = "Balance of Trade" });

            heatmap.Legend.Visibility = DevExpress.Utils.DefaultBoolean.True;

            heatmap.Label.Visible = true;
            heatmap.Label.Font = new Font("SegoeUI", 6);
            heatmap.Label.Pattern = "{V}";
            heatmap.Label.Color = Color.Black;

            heatmap.ToolTipEnabled = true;
            heatmap.ToolTipController = new DevExpress.Utils.ToolTipController {
                AllowHtmlText = true,
                ToolTipLocation = DevExpress.Utils.ToolTipLocation.RightTop,
                ShowBeak = true
            };
            heatmap.ToolTipTextPattern = "X: <b>{X}</b>\nY: <b>{Y}</b>";

            heatmap.EnableAxisXScrolling = true;
            heatmap.EnableAxisYScrolling = true;
            heatmap.EnableAxisXZooming = true;
            heatmap.EnableAxisYZooming = true;

            heatmap.AxisX.Title.Text = "Region";
            heatmap.AxisX.Title.Visibility = DevExpress.Utils.DefaultBoolean.True;
            heatmap.AxisX.Label.Staggered = false;
            heatmap.AxisX.Label.ResolveOverlappingOptions.AllowStagger = false;
            heatmap.AxisX.Label.ResolveOverlappingOptions.AllowRotate = false;
            heatmap.AxisX.Label.ResolveOverlappingOptions.AllowHide = false;
            heatmap.AxisY.Title.Text = "Product Category";
            heatmap.AxisY.Title.Visibility = DevExpress.Utils.DefaultBoolean.True;
        }

        public static DataTable CreateDataSet(string xmlFileName) {
            string filePath = GetRelativePath(xmlFileName);
            if (!string.IsNullOrWhiteSpace(filePath)) {
                DataSet dataSet = new DataSet();
                dataSet.ReadXml(filePath);
                if (dataSet.Tables.Count > 0)
                    return dataSet.Tables[0];
            }
            return null;
        }
        public static string GetRelativePath(string name) {
            name = "Data\\" + name;
            DirectoryInfo dir = new DirectoryInfo(Application.StartupPath);
            for (int i = 0; i <= 10; i++) {
                string filePath = Path.Combine(dir.FullName, name);
                if (File.Exists(filePath))
                    return filePath;
                dir = Directory.GetParent(dir.FullName);
            }
            return string.Empty;
        }
    }
}

The XML file structure looks as follows:

Show XML
<?xml version="1.0" standalone="yes"?>
<BalanceOfTrade xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:element name="Item">
      <xs:complexType>
        <xs:sequence>
          <xs:element name="Country" type="xs:string"/>
          <xs:element name="Product" type="xs:string"/>
          <xs:element name="Value" type="xs:double"/>
        </xs:sequence>
      </xs:complexType>
    </xs:element>
  </xs:schema>
  <Item>
    <Country>China</Country>
    <Product>Computer</Product>
    <Value>-151.9</Value>
  </Item>
  <Item>
    <Country>China</Country>
    <Product>Oil, Gas, Minerals</Product>
    <Value>1.9</Value>
  </Item>
  <Item>
    <Country>China</Country>
    <Product>Transportation</Product>
    <Value>10.9</Value>
  </Item>
  <Item>
    <Country>China</Country>
    <Product>Apparel</Product>
    <Value>-56.3</Value>
  </Item>
  <!--...-->
</BalanceOfTrade>     

Implements

DevExpress.XtraCharts.Heatmap.Native.IHeatmapInteractionContainer

Inheritance

See Also