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Legend in JavaScript HeatMap Chart control

26 Oct 2021 / 12 minutes to read

The legend is used to provide the information about the heat map cell. You can enable the legend by setting the visible property to true and injecting the Legend module using the HeatMap.Inject(Legend).

Source

Preview

app.ts

index.ts

index.html

import { HeatMap, Legend } from '@syncfusion/ej2-heatmap';
HeatMap.Inject(Legend);

let heatmapData: any [] = [
    [73, 39, 26, 39, 94, 0],
    [93, 58, 53, 38, 26, 68],
    [99, 28, 22, 4, 66, 90],
    [14, 26, 97, 69, 69, 3],
    [7, 46, 47, 47, 88, 6],
    [41, 55, 73, 23, 3, 79],
    [56, 69, 21, 86, 3, 33],
    [45, 7, 53, 81, 95, 79],
    [60, 77, 74, 68, 88, 51],
    [25, 25, 10, 12, 78, 14],
    [25, 56, 55, 58, 12, 82],
    [74, 33, 88, 23, 86, 59]
];

let heatmap: HeatMap = new HeatMap({
    titleSettings: {
        text: 'Sales Revenue per Employee (in 1000 US$)',
        textStyle: {
            size: '15px',
            fontWeight: '500',
            fontStyle: 'Normal',
            fontFamily: 'Segoe UI'
            }
        },
        xAxis: {
            labels: ['Nancy', 'Andrew', 'Janet', 'Margaret', 'Steven',
            'Michael', 'Robert', 'Laura', 'Anne', 'Paul', 'Karin',   'Mario'],
        },
        yAxis: {
            labels: ['Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat'],
        },
        cellSettings: {
            showLabel: false,
        },
        paletteSettings: {
        palette: [
           { value: 0, color: '#C2E7EC' },
            { value: 10, color: '#AEDFE6' },
            { value: 20, color: '#9AD7E0' },
            { value: 30, color: '#72C7D4' },
            { value: 40, color: '#5EBFCE' },
            { value: 50, color: '#4AB7C8' },
            { value: 60, color: '#309DAE' },
            { value: 70, color: '#2B8C9B' },
            { value: 80, color: '#206974' },
            { value: 90, color: '#15464D' },
            { value: 100, color: '#000000' },
        ],
        },
        dataSource: heatmapData,
        legendSettings: {
            position: 'Right',
        }
});
heatmap.appendTo('#element');

<!DOCTYPE html>
<html lang="en">

<head>
    <title>EJ2 HeatMap</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Typescript UI Controls" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='element'></div>
    </div>
</body>

</html>

Legend types

Heat map supports two legend types: Gradient and list type.

Gradient: This is a continuous color legend with smooth color transition between palette color values.
List: List is a fixed color legend. Each palette color information is shown separately in the list item.

You can change the legend type by using the type property in the paletteSettings property.

Source

Preview

app.ts

index.ts

index.html

import { HeatMap, Legend } from '@syncfusion/ej2-heatmap';
HeatMap.Inject(Legend);

let heatmapData: any [] = [
[73, 39, 26, 39, 94, 0],
[93, 58, 53, 38, 26, 68],
[99, 28, 22, 4, 66, 90],
[14, 26, 97, 69, 69, 3],
[7, 46, 47, 47, 88, 6],
[41, 55, 73, 23, 3, 79],
[56, 69, 21, 86, 3, 33],
[45, 7, 53, 81, 95, 79],
[60, 77, 74, 68, 88, 51],
[25, 25, 10, 12, 78, 14],
[25, 56, 55, 58, 12, 82],
[74, 33, 88, 23, 86, 59]];

let heatmap: HeatMap = new HeatMap({
titleSettings: {
        text: 'Sales Revenue per Employee (in 1000 US$)',
        textStyle: {
            size: '15px',
            fontWeight: '500',
            fontStyle: 'Normal',
            fontFamily: 'Segoe UI'
        }
    },
    xAxis: {
        labels: ['Nancy', 'Andrew', 'Janet', 'Margaret', 'Steven',
        'Michael', 'Robert', 'Laura', 'Anne', 'Paul', 'Karin',   'Mario'],
    },
    yAxis: {
        labels: ['Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat'],
    },
    cellSettings: {
        showLabel: false,
    },
    paletteSettings: {
        type: 'Fixed'
    },
    dataSource: heatmapData,
    legendSettings: {
        position: 'Right',
    }
});
heatmap.appendTo('#element');

<!DOCTYPE html>
<html lang="en">

<head>
    <title>EJ2 HeatMap</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Typescript UI Controls" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='element'></div>
    </div>
</body>

</html>

Placement

You can place the legend at left, right, top, or bottom to the heat map layout by using the position property. The legend is positioned at the right to the heat map by default.

Source

Preview

app.ts

index.ts

index.html

import { HeatMap, Legend } from '@syncfusion/ej2-heatmap';
HeatMap.Inject(Legend);

let heatmapData: any [] = [
[73, 39, 26, 39, 94, 0],
[93, 58, 53, 38, 26, 68],
[99, 28, 22, 4, 66, 90],
[14, 26, 97, 69, 69, 3],
[7, 46, 47, 47, 88, 6],
[41, 55, 73, 23, 3, 79],
[56, 69, 21, 86, 3, 33],
[45, 7, 53, 81, 95, 79],
[60, 77, 74, 68, 88, 51],
[25, 25, 10, 12, 78, 14],
[25, 56, 55, 58, 12, 82],
[74, 33, 88, 23, 86, 59]];

let heatmap: HeatMap = new HeatMap({
titleSettings: {
        text: 'Sales Revenue per Employee (in 1000 US$)',
        textStyle: {
            size: '15px',
            fontWeight: '500',
            fontStyle: 'Normal',
            fontFamily: 'Segoe UI'
        }
    },
    xAxis: {
        labels: ['Nancy', 'Andrew', 'Janet', 'Margaret', 'Steven',
        'Michael', 'Robert', 'Laura', 'Anne', 'Paul', 'Karin',   'Mario'],
    },
    yAxis: {
        labels: ['Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat'],
    },
    dataSource: heatmapData,
    legendSettings: {
        position: 'Top',
    }
});
heatmap.appendTo('#element');

<!DOCTYPE html>
<html lang="en">

<head>
    <title>EJ2 HeatMap</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Typescript UI Controls" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='element'></div>
    </div>
</body>

</html>

Alignment

You can align the legend as center, far, or near to the heat map using the alignment property.

Source

Preview

app.ts

index.ts

index.html

import { HeatMap, Legend } from '@syncfusion/ej2-heatmap';
HeatMap.Inject(Legend);

let heatmapData: any [] = [
[73, 39, 26, 39, 94, 0],
[93, 58, 53, 38, 26, 68],
[99, 28, 22, 4, 66, 90],
[14, 26, 97, 69, 69, 3],
[7, 46, 47, 47, 88, 6],
[41, 55, 73, 23, 3, 79],
[56, 69, 21, 86, 3, 33],
[45, 7, 53, 81, 95, 79],
[60, 77, 74, 68, 88, 51],
[25, 25, 10, 12, 78, 14],
[25, 56, 55, 58, 12, 82],
[74, 33, 88, 23, 86, 59]];

let heatmap: HeatMap = new HeatMap({
titleSettings: {
        text: 'Sales Revenue per Employee (in 1000 US$)',
        textStyle: {
            size: '15px',
            fontWeight: '500',
            fontStyle: 'Normal',
            fontFamily: 'Segoe UI'
        }
    },
    xAxis: {
        labels: ['Nancy', 'Andrew', 'Janet', 'Margaret', 'Steven',
        'Michael', 'Robert', 'Laura', 'Anne', 'Paul', 'Karin',   'Mario'],
    },
    yAxis: {
        labels: ['Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat'],
    },
    dataSource: heatmapData,
    legendSettings: {
        position: 'Right',
        alignment: 'Near',
        height: '150px'
    }
});
heatmap.appendTo('#element');

<!DOCTYPE html>
<html lang="en">

<head>
    <title>EJ2 HeatMap</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Typescript UI Controls" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='element'></div>
    </div>
</body>

</html>

Legend dimensions

You can change the legend dimensions with values in pixels or percentage by using the width and height properties.

Source

Preview

app.ts

index.ts

index.html

import { HeatMap, Legend } from '@syncfusion/ej2-heatmap';
HeatMap.Inject(Legend);

let heatmapData: any [] = [
[73, 39, 26, 39, 94, 0],
[93, 58, 53, 38, 26, 68],
[99, 28, 22, 4, 66, 90],
[14, 26, 97, 69, 69, 3],
[7, 46, 47, 47, 88, 6],
[41, 55, 73, 23, 3, 79],
[56, 69, 21, 86, 3, 33],
[45, 7, 53, 81, 95, 79],
[60, 77, 74, 68, 88, 51],
[25, 25, 10, 12, 78, 14],
[25, 56, 55, 58, 12, 82],
[74, 33, 88, 23, 86, 59]];

let heatmap: HeatMap = new HeatMap({
titleSettings: {
        text: 'Sales Revenue per Employee (in 1000 US$)',
        textStyle: {
            size: '15px',
            fontWeight: '500',
            fontStyle: 'Normal',
            fontFamily: 'Segoe UI'
        }
    },
    xAxis: {
        labels: ['Nancy', 'Andrew', 'Janet', 'Margaret', 'Steven',
        'Michael', 'Robert', 'Laura', 'Anne', 'Paul', 'Karin',   'Mario'],
    },
    yAxis: {
        labels: ['Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat'],
    },
    dataSource: heatmapData,
    legendSettings: {
        position: 'Right',
        height: '150px',
    }
});
heatmap.appendTo('#element');

<!DOCTYPE html>
<html lang="en">

<head>
    <title>EJ2 HeatMap</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Typescript UI Controls" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='element'></div>
    </div>
</body>

</html>

Paging for legend

Paging is available only for the list type legend in the heat map, and it can be enabled by default, when the legend items exceed the legend bounds. You can view each legend items by navigating between the pages using navigation buttons.

Source

Preview

app.ts

index.ts

index.html

import { HeatMap, Legend } from '@syncfusion/ej2-heatmap';
HeatMap.Inject(Legend);

let heatmapData: any [] = [
[73, 39, 26, 39, 94, 0],
[93, 58, 53, 38, 26, 68],
[99, 28, 22, 4, 66, 90],
[14, 26, 97, 69, 69, 3],
[7, 46, 47, 47, 88, 6],
[41, 55, 73, 23, 3, 79],
[56, 69, 21, 86, 3, 33],
[45, 7, 53, 81, 95, 79],
[60, 77, 74, 68, 88, 51],
[25, 25, 10, 12, 78, 14],
[25, 56, 55, 58, 12, 82],
[74, 33, 88, 23, 86, 59]
];

let heatmap: HeatMap = new HeatMap({
titleSettings: {
    text: 'Sales Revenue per Employee (in 1000 US$)',
    textStyle: {
        size: '15px',
        fontWeight: '500',
        fontStyle: 'Normal',
        fontFamily: 'Segoe UI'
        }
    },
    xAxis: {
        labels: ['Nancy', 'Andrew', 'Janet', 'Margaret', 'Steven',
        'Michael', 'Robert', 'Laura', 'Anne', 'Paul', 'Karin',   'Mario'],
    },
    yAxis: {
        labels: ['Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat'],
    },
    paletteSettings: {
    palette: [
       { value: 0, color: '#C2E7EC' },
        { value: 10, color: '#AEDFE6' },
        { value: 20, color: '#9AD7E0' },
        { value: 25, color: '#86CFDA' },
        { value: 30, color: '#72C7D4' },
        { value: 40, color: '#5EBFCE' },
        { value: 50, color: '#4AB7C8' },
        { value: 55, color: '#36AFC2' },
        { value: 60, color: '#309DAE' },
        { value: 70, color: '#2B8C9B' },
        { value: 75, color: '#257A87' },
        { value: 80, color: '#206974' },
        { value: 85, color: '#1B5761' },
        { value: 90, color: '#15464D' },
        { value: 100, color: '#000000' },
    ],
        type: 'Fixed'
    },
    dataSource: heatmapData,
    legendSettings: {
        position: 'Right',
        height: "150px"
    }
});
heatmap.appendTo('#element');

<!DOCTYPE html>
<html lang="en">

<head>
    <title>EJ2 HeatMap</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Typescript UI Controls" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='element'></div>
    </div>
</body>

</html>

Note: To use legend feature, we need to inject Legend using HeatMap.Inject(Legend).

Smart Legend

Smart legend is another way of showing list type legend with responsiveness and readability, when the palette has more number of items. You can enable this smart legend by using the enableSmartLegend property when the palette type is set to Fixed.

In smart legend, you can change the display type of legend labels by using the labelDisplayType property.

The following are the legend label display types:

All: Displays all labels in the legend.
Edge: Displays the legend labels only at extreme ends.
None: None of the labels are displayed. The tooltip will appear for this type of label display when hovering over the legend item.

Source

Preview

app.ts

index.ts

index.html

import { HeatMap, Legend } from '@syncfusion/ej2-heatmap';
HeatMap.Inject(Legend);

let heatmapData: any [] = [
[73, 39, 26, 39, 94, 0],
[93, 58, 53, 38, 26, 68],
[99, 28, 22, 4, 66, 90],
[14, 26, 97, 69, 69, 3],
[7, 46, 47, 47, 88, 6],
[41, 55, 73, 23, 3, 79],
[56, 69, 21, 86, 3, 33],
[45, 7, 53, 81, 95, 79],
[60, 77, 74, 68, 88, 51],
[25, 25, 10, 12, 78, 14],
[25, 56, 55, 58, 12, 82],
[74, 33, 88, 23, 86, 59]];

let heatmap: HeatMap = new HeatMap({
titleSettings: {
        text: 'Sales Revenue per Employee (in 1000 US$)',
        textStyle: {
            size: '15px',
            fontWeight: '500',
            fontStyle: 'Normal',
            fontFamily: 'Segoe UI'
        }
    },
    xAxis: {
        labels: ['Nancy', 'Andrew', 'Janet', 'Margaret', 'Steven',
        'Michael', 'Robert', 'Laura', 'Anne', 'Paul', 'Karin', 'Mario'],
    },
    yAxis: {
        labels: ['Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat'],
    },
    cellSettings: {
        showLabel: false,
    },
    paletteSettings: {
        palette: [
        { value: 0, color: '#C2E7EC' },
        { value: 10, color: '#AEDFE6' },
        { value: 20, color: '#9AD7E0' },
        { value: 30, color: '#72C7D4' },
        { value: 40, color: '#5EBFCE' },
        { value: 50, color: '#4AB7C8' },
        { value: 60, color: '#309DAE' },
        { value: 70, color: '#2B8C9B' },
        { value: 80, color: '#206974' },
        { value: 90, color: '#15464D' },
        { value: 100, color: '#000000' },
    ],
        type: 'Fixed'
    },
    dataSource: heatmapData,
    legendSettings: {
        position: 'Bottom',
        width: '75%',
        enableSmartLegend: true
    }
});
heatmap.appendTo('#element');

<!DOCTYPE html>
<html lang="en">

<head>
    <title>EJ2 HeatMap</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Typescript UI Controls" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='element'></div>
    </div>
</body>

</html>

Legend Selection

In the HeatMap, the legend selection is used to toggle the visibility of cell for view the specific range value. You can enable the legend selection using toggleVisibility.

Source

Preview

app.ts

index.ts

index.html

import { HeatMap, Legend } from '@syncfusion/ej2-heatmap';
HeatMap.Inject(Legend);

let heatmapData: any [] = [
[73, 39, 26, 39, 94, 0],
[93, 58, 53, 38, 26, 68],
[99, 28, 22, 4, 66, 90],
[14, 26, 97, 69, 69, 3],
[7, 46, 47, 47, 88, 6],
[41, 55, 73, 23, 3, 79],
[56, 69, 21, 86, 3, 33],
[45, 7, 53, 81, 95, 79],
[60, 77, 74, 68, 88, 51],
[25, 25, 10, 12, 78, 14],
[25, 56, 55, 58, 12, 82],
[74, 33, 88, 23, 86, 59]];

let heatmap: HeatMap = new HeatMap({
titleSettings: {
        text: 'Sales Revenue per Employee (in 1000 US$)',
        textStyle: {
            size: '15px',
            fontWeight: '500',
            fontStyle: 'Normal',
            fontFamily: 'Segoe UI'
        }
    },
    xAxis: {
        labels: ['Nancy', 'Andrew', 'Janet', 'Margaret', 'Steven',
        'Michael', 'Robert', 'Laura', 'Anne', 'Paul', 'Karin', 'Mario'],
    },
    yAxis: {
        labels: ['Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat'],
    },
    cellSettings: {
        showLabel: false,
    },
    paletteSettings: {
        palette: [
        { value: 0, color: '#C2E7EC' },
        { value: 10, color: '#AEDFE6' },
        { value: 20, color: '#9AD7E0' },
        { value: 30, color: '#72C7D4' },
        { value: 40, color: '#5EBFCE' },
        { value: 50, color: '#4AB7C8' },
        { value: 60, color: '#309DAE' },
        { value: 70, color: '#2B8C9B' },
        { value: 80, color: '#206974' },
        { value: 90, color: '#15464D' },
        { value: 100, color: '#000000' },
    ],
        type: 'Fixed'
    },
    dataSource: heatmapData,
    legendSettings: {
        position: 'Bottom',
        width: '75%',
        enableSmartLegend: true,
        toggleVisibility: true
    }
});
  heatmap.appendTo('#element');

<!DOCTYPE html>
<html lang="en">

<head>
    <title>EJ2 HeatMap</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Typescript UI Controls" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='element'></div>
    </div>
</body>

</html>

Legend Title

The legend title displays a specific information about the legend. You can enable the legend title by setting the title property by providing the text and customizing the legend title text style using the textStyle property.

Source

Preview

app.ts

index.ts

index.html

import { HeatMap, Legend } from '@syncfusion/ej2-heatmap';
HeatMap.Inject(Legend);

let heatmapData: any [] = [
[73, 39, 26, 39, 94, 0],
[93, 58, 53, 38, 26, 68],
[99, 28, 22, 4, 66, 90],
[14, 26, 97, 69, 69, 3],
[7, 46, 47, 47, 88, 6],
[41, 55, 73, 23, 3, 79],
[56, 69, 21, 86, 3, 33],
[45, 7, 53, 81, 95, 79],
[60, 77, 74, 68, 88, 51],
[25, 25, 10, 12, 78, 14],
[25, 56, 55, 58, 12, 82],
[74, 33, 88, 23, 86, 59]
];

let heatmap: HeatMap = new HeatMap({
titleSettings: {
    text: 'Sales Revenue per Employee'
    },
    xAxis: {
        labels: ['Nancy', 'Andrew', 'Janet', 'Margaret', 'Steven',
        'Michael', 'Robert', 'Laura', 'Anne', 'Paul', 'Karin',   'Mario'],
    },
    yAxis: {
        labels: ['Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat'],
    },
    cellSettings: {
        showLabel: false,
    },
    paletteSettings: {
    palette: [
        { value: 0, color: '#6EB5D0' },
        { value: 50, color: '#7EDCA2' },
        { value: 100, color: '#DCD57E' },
    ],
    },
    dataSource: heatmapData,
    legendSettings: {
        position: 'Right',
        title: {
            text: "1000 US$"
        }
    }
});
heatmap.appendTo('#element');

<!DOCTYPE html>
<html lang="en">

<head>
    <title>EJ2 HeatMap</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Typescript UI Controls" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='element'></div>
    </div>
</body>

</html>

Contents

Legend types
Placement
Alignment
Legend dimensions
Paging for legend
Smart Legend
Legend Selection
Legend Title

Contents

Legend types
Placement
Alignment
Legend dimensions
Paging for legend
Smart Legend
Legend Selection
Legend Title