Prevent crowded labels in the Chart

Environment

Product Chart for Blazor

Description

I am having a Chart with big load of data. The labels are overlapping and thus - unreadable.

Solution

You can control how many labels render, their rotation angle and even font in order to reduce clutter. Read further to see how to find and use the appropriate tags and parameters.

You can also skip directly to the examples:

The general approach to customize the Chart is to apply settings using nested tags. In the case of the Labels the tag is

  • for categorical charts - <ChartCategoryAxisLabels> under the <ChartCategoryAxis>.
  • for numerical charts - <ChartXAxisLabels> and <ChartYAxisLabels> under the <ChartXAxis> and <ChartYAxis>.

You can control the Labels by applying the following settings to the <ChartCategoryAxisLabels> or <ChartXAxisLabels> tags depending on the Chart type:

  • Angle - rotate the Labels to a desired degree - can be useful for long texts even if you have few items
  • Step - skip the rendering of every n-th label, where n is the double number passed to the parameter.
  • Skip - skip the rendering of the first n labels, where n is the double number passed to the parameter.

To rotate the Labels to a desired degree you can use the Angle setting of the <ChartCategoryAxisLabelsRotation />, nested tag of <ChartXAxisLabelsRotation />, or <ChartYAxisLabelsRotation /> respectively for categorical and numerical charts.

To skip the rendering of every n-th label, when the data in your application allows it (e.g., for a date axis or numerical axes), you can use the Step setting of the <ChartCategoryAxisLabels> or <ChartXAxisLabels>. Applying that would notify the chart to skip every n-th label, for example if set to 2 only the even labels would be rendered.

You can also control other visual settings of the Labels such as Padding, Borders and Margin by using the respective nested tags - <ChartCategoryAxisLabels<SETTING NAME> />. The labels also have a Font parameter where you can pass a CSS font setting to reduce the size of the text.

Example - Rotate the Chart Labels

@* This example shows how to rotate the labels of a Categorical Chart by a certain angle *@

<TelerikChart>
    <ChartSeriesItems>
        <ChartSeries Type="ChartSeriesType.Column" Name="Product 1" Data="@series1Data">
        </ChartSeries>
        <ChartSeries Type="ChartSeriesType.Column" Name="Product 2" Data="@series2Data">
        </ChartSeries>
    </ChartSeriesItems>

    <ChartCategoryAxes>
        <ChartCategoryAxis Categories="@xAxisItems">
            <ChartCategoryAxisLabels>
                <ChartCategoryAxisLabelsRotation Angle="-45" />
            </ChartCategoryAxisLabels>
        </ChartCategoryAxis>
    </ChartCategoryAxes>

    <ChartTitle Text="Quarterly revenue per product"></ChartTitle>

    <ChartLegend Position="ChartLegendPosition.Right">
    </ChartLegend>
</TelerikChart>

@code {
    public List<object> series1Data = new List<object>() { 10, 2, 5, 6, 8, 8, 13, 11, 4, 9, 10, 15, 14, 3, 2 };
    public List<object> series2Data = new List<object>() { 5, 8, 2, 7, 6, 11, 14, 13, 8, 7, 2, 7, 5, 9, 11 };
    public string[] xAxisItems = new string[15];

    protected override void OnInitialized()
    {
        for (int i = 0; i < 15; i++)
        {
            xAxisItems[i] = $"looooong label {i + 1}";
        }
        base.OnInitialized();
    }
}

The result from the code snippet above

rotate chart labels

Example - Skip rendering every n-th label

@* This example shows how render only every third label *@

<TelerikChart>
    <ChartSeriesItems>
        <ChartSeries Type="ChartSeriesType.Column" Name="Product 1" Data="@series1Data">
        </ChartSeries>
        <ChartSeries Type="ChartSeriesType.Column" Name="Product 2" Data="@series2Data">
        </ChartSeries>
    </ChartSeriesItems>

    <ChartCategoryAxes>
        <ChartCategoryAxis Categories="@xAxisItems">
            <ChartCategoryAxisLabels Step="3">
            </ChartCategoryAxisLabels>
        </ChartCategoryAxis>
    </ChartCategoryAxes>

    <ChartTitle Text="Quarterly revenue per product"></ChartTitle>

    <ChartLegend Position="ChartLegendPosition.Right">
    </ChartLegend>
</TelerikChart>

@code {
    public List<object> series1Data = new List<object>() { 10, 2, 5, 6, 8, 8, 13, 11, 4, 9, 10, 15, 14, 3, 2 };
    public List<object> series2Data = new List<object>() { 5, 8, 2, 7, 6, 11, 14, 13, 8, 7, 2, 7, 5, 9, 11 };
    public string[] xAxisItems = new string[15];

    protected override void OnInitialized()
    {
        for (int i = 0; i < 15; i++)
        {
            xAxisItems[i] = $"looooong label {i + 1}";
        }
    }
}

The result from the code snippet above

rotate chart labels

Notes

You can also see the Knowledge base article regarding clustered grid lines to further improve the layout of the Chart.

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