Axis Labels

Jun 18, 2024
7 minutes to read

The Chart Control can display default and custom axis labels. Default labels are generated based on series data.

The Chart Control automatically calculates the grid layout so that certain axis labels are hidden depending on the actual chart size to avoid overlapping labels.

The following image illustrates the chart layout with hidden X-Axis labels (region):

To display all axis labels, disable the scale’s AutoGrid option and set the GridSpacing property to 1.

Configure Custom Labels

You can create custom axis labels and modify their position and content. The Chart Control can display custom and default labels simultaneously. The following image shows custom axis labels for a Y-axis:

Use the markup below to configure custom axis labels:

XAML

xaml

<dxc:XYDiagram2D.AxisY>
      <dxc:AxisY2D LabelVisibilityMode="Default"
                   GridLinesMinorVisible="False" 
                   Interlaced="False" 
                   Brush="Transparent">
            <dxc:AxisY2D.CustomLabels>
                  <dxc:CustomAxisLabel Value="120" Content="2h"/>
                  <dxc:CustomAxisLabel Value="360" Content="6h"/>
                  <dxc:CustomAxisLabel Value="600" Content="10h"/>
                  <dxc:CustomAxisLabel Value="840" Content="14h"/>
            </dxc:AxisY2D.CustomLabels>
      </dxc:AxisY2D>
</dxc:XYDiagram2D.AxisY>

This code uses the following API members:

Class or Property	Description
Axis2D.CustomLabels	The custom axis labels’ collection. If this collection is empty, the Chart Control displays default axis labels.
CustomAxisLabel	A custom axis label.
CustomAxisLabel.Value	A value that specifies a label position along an axis.
CustomAxisLabel.Content	Custom label content.
Axis2D.LabelVisibilityMode	Specifies whether to show custom and default axis labels simultaneously.

If the Axis2D.CustomLabels collection does not contain any visible custom labels, the default axis labels are shown. Set the Axis2D.LabelVisibilityMode property to AutoGeneratedAndCustom to display custom and default labels simultaneously.

How to Use the MVVM Design Pattern

To generate custom axis labels from a ViewModel, bind the Axis2D.CustomLabelItemsSource property to a collection of objects that contain label parameters. Use the Axis2D.CustomLabelItemTemplate or Axis2D.CustomLabelItemTemplateSelector property to specify how to convert a model object to a custom label.

The following example shows how to generate custom labels for a y-axis:

XAML

xaml

<Window.DataContext> 
    <local:MainViewModel/> 
</Window.DataContext> 

<dxc:XYDiagram2D.AxisY> 
    <dxc:AxisY2D x:Name="axisY" 
                 GridLinesMinorVisible="False" 
                 Interlaced="False" 
                 Brush="Transparent" 
                 CustomLabelItemsSource="{Binding CustomLabels}"> 
        <dxc:AxisY2D.CustomLabelItemTemplate> 
            <DataTemplate> 
                <dxc:CustomAxisLabel Value="{Binding Item1}" 
                                     Content="{Binding Item2}"/> 
            </DataTemplate> 
        </dxc:AxisY2D.CustomLabelItemTemplate> 
    </dxc:AxisY2D> 
</dxc:XYDiagram2D.AxisY>

C#
VB.NET

csharp

public class MainViewModel {
    public IEnumerable<Tuple<double, string>> CustomLabels { get; private set; }
    public MainViewModel() {
        this.CustomLabels = new List<Tuple<double, string>> {
            new Tuple<double, string>(120, "2h"),
            new Tuple<double, string>(360, "6h"),
            new Tuple<double, string>(600, "10h"),
            new Tuple<double, string>(840, "14h")
        };
    }
}

Public Class MainViewModel    
    Public Property CustomLabels As IEnumerable(Of Tuple)
        Get 
        End Get 
        Set 
        End Set 
    End Property 
    Public Sub New()
        MyBase.New 
        Me.CustomLabels = New List(Of Tuple)() {
                         New Tuple(Of Double, String)(120, "2h"), 
                         New Tuple(Of Double, String)(360, "6h"), 
                         New Tuple(Of Double, String)(600, "10h"), 
                         New Tuple(Of Double, String)(840, "14h")}
    End Sub 
End Class

The code above uses the following API members:

Member	Description
Axis2D.CustomLabelItemsSource	Gets or sets the collection that is used to generate custom labels.
Axis2D.CustomLabelItemTemplate	Specifies the DataTemplate object that defines how to convert a model object to a custom label.
Axis2D.CustomLabelItemTemplateSelector	Gets or sets the DataTemplateSelector object that defines the custom logic to select a data template that converts a model to a custom label.

How to Format Default Label Text

Use the predefined placeholders, format specifiers, and plain text to set a pattern that defines a label’s text. In the image below, the {V} min pattern is applied to the y-axis labels.

The following markup configures the label’s text pattern:

XAML

xaml

<dxc:XYDiagram2D.AxisY>
      <dxc:AxisY2D GridLinesMinorVisible="False" 
                   Interlaced="False" 
                   Brush="Transparent">
            <dxc:AxisY2D.Label>
                  <dxc:AxisLabel TextPattern="{}{V} min"/>
            </dxc:AxisY2D.Label>
      </dxc:AxisY2D>
</dxc:XYDiagram2D.AxisY>

The code above uses the classes and properties from the table below:

Class or Property	Description
AxisLabel.TextPattern	Specifies the text pattern.
AxisBase.Label	Specifies label settings.
AxisLabel	The axis label settings’ storage.

The following table lists all available placeholders:

Pattern	Description
{A}	Displays series point arguments (only for argument axes).
{V}	Displays series point values (only for value axes).
{VP}	Displays series point values as a percentage (only for value axes).

You can also specify the AxisLabel.Formatter property to generate text strings for axis labels based on a custom condition or change the order of magnitude of axis label values. If the Formatter property is specified, the AxisLabel.TextPattern value is ignored.

TextPattern can be applied to date-time or numeric scale values. Use Formatter for the qualitative scale type.

Follow the steps below to create a formatter:

Create a class that inherits the IAxisLabelFormatter interface and implement the GetAxisLabelText method.
Assign the newly created class instance to the AxisLabel.Formatter property.

This example shows how to apply a custom format to numeric axis labels:

A formatter applies to axis labels:

A formatter does not apply to axis labels:

Markup:

XAML

xaml

<dxc:XYDiagram2D.AxisX>
    <dxc:AxisX2D>
        <dxc:AxisX2D.Label>
            <dxc:AxisLabel>
                <dxc:AxisLabel.Formatter>
                    <local:AxisLabelFormatter/>
                </dxc:AxisLabel.Formatter>
            </dxc:AxisLabel>
        </dxc:AxisX2D.Label>
    </dxc:AxisX2D>
</dxc:XYDiagram2D.AxisX>
<dxc:XYDiagram2D.AxisY>
    <dxc:AxisY2D>
            <dxc:AxisLabel>
                <dxc:AxisLabel.Formatter>
                    <local:AxisLabelFormatter/>
                </dxc:AxisLabel.Formatter>
            </dxc:AxisLabel>
        </dxc:AxisY2D.Label>
    </dxc:AxisY2D>
</dxc:XYDiagram2D.AxisY>

Code-Behind:

C#
VB.NET

csharp

public class AxisLabelFormatter : IAxisLabelFormatter {
    public string GetAxisLabelText(object axisValue) {
        return Convert.ToString((double)axisValue / 1000);
    }
}

Public Class AxisLabelFormatter
    Inherits IAxisLabelFormatter
    Public Function GetAxisLabelText(ByVal axisValue As Object) As String
        Return Convert.ToString(CDbl(axisValue) / 1000)
    End Function
End Class

Resolve Axis Label Overlap

The Chart Control includes a Resolve Overlap algorithm that rotates, staggers and hides axis labels when they cannot sufficiently display label content due to lack of space. You can use the Resolve Overlap options to configure this algorithm. The image below shows a chart with these options disabled.

The following animation shows how the Resolve Overlap algorithm works:

The example below configures the Resolve Overlap algorithm options:

View Example: Configure Resolve Overlapping for Axis Labels

XAML

xaml

<dxc:XYDiagram2D.AxisX>
    <dxc:AxisX2D>
        <dxc:AxisX2D.DateTimeScaleOptions>
            <dxc:ManualDateTimeScaleOptions MeasureUnit="Hour"
                        GridAlignment="Hour"
                        GridSpacing="6"
                        AutoGrid="False" />
        </dxc:AxisX2D.DateTimeScaleOptions>
        <dxc:AxisX2D.Label>
            <dxc:AxisLabel TextPattern="{}{A:dd/MM HH:mm}">
                <dxc:Axis2D.ResolveOverlappingOptions>
                    <dxc:AxisLabelResolveOverlappingOptions AllowHide="True"
                                AllowRotate="True"
                                AllowStagger="True"
                                MinIndent="5" />
                </dxc:Axis2D.ResolveOverlappingOptions>
            </dxc:AxisLabel>
        </dxc:AxisX2D.Label>
    </dxc:AxisX2D>
</dxc:XYDiagram2D.AxisX>

The code above uses the following API members:

Member	Description
Axis2D.ResolveOverlappingOptions	Settings that define how to resolve label overlap.
AxisLabelResolveOverlappingOptions.AllowHide	Gets or sets the value that indicates whether to hide axis labels to resolve overlap.
AxisLabelResolveOverlappingOptions.AllowRotate	Specifies the value that indicates whether to rotate axis labels.
AxisLabelResolveOverlappingOptions.AllowStagger	Gets or sets the value that indicates whether to stagger axis labels.
AxisLabelResolveOverlappingOptions.MinIndent	Gets or sets the minimum indent between adjacent axis labels when the Resolve Overlap algorithm is applied.

Note

The AllowRotate and AllowStagger properties only affect labels of a horizontal 2D XY Diagram axis (the argument x-axis, or the value y-axis when XYDiagram2D.Rotated is set to true ).

The following example uses the Axis2D.SetResolveOverlappingOptions method to specify the Resolve Overlap options for an X-axis in code:

C#
VB.NET

csharp

AxisLabel xLabel = new AxisLabel();
Axis2D.SetResolveOverlappingOptions(xLabel, new AxisLabelResolveOverlappingOptions() { AllowHide = false,
                                                                                       AllowRotate = false,
                                                                                       AllowStagger = false});
((XYDiagram2D)chartControl1.Diagram).ActualAxisX.Label = xLabel;

Dim xLabel As AxisLabel = New AxisLabel()
Axis2D.SetResolveOverlappingOptions(xLabel, New AxisLabelResolveOverlappingOptions() With {
        .AllowHide = False,
        .AllowRotate = False,
        .AllowStagger = False
})
CType(chartControl1.Diagram, XYDiagram2D).ActualAxisX.Label = xLabel

Customize Label Appearance

You can change the text color, background color, font, and orientation of axis labels.

In Markup

XAML

xaml

<dxc:XYDiagram2D.AxisX>
    <dxc:AxisX2D Visible="True">
        <dxc:AxisX2D.Label>
            <dxc:AxisLabel Foreground="DarkSlateBlue" 
                           Background="LightBlue" 
                           FontSize="14" 
                           FontStyle="Italic" 
                           FontWeight="Bold"
                           Angle="45"
                           TextPattern="{}{V} year"/>
        </dxc:AxisX2D.Label>
    </dxc:AxisX2D>
</dxc:XYDiagram2D.AxisX>

In Code-Behind

C#
VB.NET

csharp

XYDiagram2D diagram = (XYDiagram2D)chartControl1.Diagram;
diagram.AxisX = new AxisX2D();
diagram.AxisX.Label = new AxisLabel();
diagram.AxisX.Label.Background = new SolidColorBrush(Colors.Orange);
diagram.AxisX.Label.Foreground = new SolidColorBrush(Colors.DarkSlateBlue);
diagram.AxisX.Label.FontSize= 14;
diagram.AxisX.Label.FontStyle = FontStyles.Italic;
diagram.AxisX.Label.FontWeight = FontWeights.Bold;

Dim diagram As XYDiagram2D = CType(chartControl1.Diagram, XYDiagram2D)
diagram.AxisX = New AxisX2D
diagram.AxisX.Label = New AxisLabel
diagram.AxisX.Label.Background = New SolidColorBrush(Colors.Orange)
diagram.AxisX.Label.Foreground = New SolidColorBrush(Colors.DarkSlateBlue)
diagram.AxisX.Label.FontSize = 14
diagram.AxisX.Label.FontStyle = FontStyles.Italic
diagram.AxisX.Label.FontWeight = FontWeights.Bold

The following appearance customization properties are available:

Angle (also specifies rotation for a data template defined in the AxisLabel.ElementTemplate property.)
Background
BorderBrush
BorderThickness
FontFamily
FontSize
FontStretch
FontStyle
FontWeight
Foreground
Padding

You can also define the ElementTemplate property to change axis label appearance:

XAML

xaml

<Window.Resources>
    <DataTemplate x:Key="AxisXLabelTemplate">
        <Border BorderThickness="1" CornerRadius="9" Opacity="1.0">
            <Border.Background>
                <SolidColorBrush Color="Orange"/>
            </Border.Background>
            <Label Content="{Binding Path=Content}" Padding="5,1,5,1.5" 
                   Foreground="DarkSlateBlue" FontSize="12" />
        </Border>
    </DataTemplate>
</Window.Resources>
...
<dxc:XYDiagram2D.AxisX>
    <dxc:AxisX2D Visible="True">
        <dxc:AxisX2D.Label>
            <dxc:AxisLabel ElementTemplate="{StaticResource AxisXLabelTemplate}"/>
        </dxc:AxisX2D.Label>
    </dxc:AxisX2D>
</dxc:XYDiagram2D.AxisX>