Polar Area

Polar Area

Polar area charts are similar to pie charts, but each segment has the same angle - the radius of the segment differs depending on the value.

This type of chart is often useful when we want to show a comparison data similar to a pie chart, but also show a scale of values for context.

Example Usage

new Chart(ctx, {
    data: data,
    type: 'polarArea',
    options: options
});

Dataset Properties

The following options can be included in a polar area chart dataset to configure options for that specific dataset.

Name	Type	Scriptable	Indexable	Default
`backgroundColor`	`Color`	Yes	Yes	`‘rgba(0, 0, 0, 0.1)’`
`borderAlign`	`string`	Yes	Yes	`‘center’`
`borderColor`	`Color`	Yes	Yes	`‘#fff’`
`borderWidth`	`number`	Yes	Yes	`2`
`data`	`number[]`	-	-	required
`hoverBackgroundColor`	`Color`	Yes	Yes	`undefined`
`hoverBorderColor`	`Color`	Yes	Yes	`undefined`
`hoverBorderWidth`	`number`	Yes	Yes	`undefined`

Styling

The style of each arc can be controlled with the following properties:

Name	Description
`backgroundColor`	arc background color.
`borderColor`	arc border color.
`borderWidth`	arc border width (in pixels).

All these values, if undefined, fallback to the associated elements.arc.* options.

Border Alignment

The following values are supported for borderAlign.

'center' (default)
'inner'

When 'center' is set, the borders of arcs next to each other will overlap. When 'inner' is set, it is guaranteed that all the borders are not overlap.

Interactions

The interaction with each arc can be controlled with the following properties:

Name	Description
`hoverBackgroundColor`	arc background color when hovered.
`hoverBorderColor`	arc border color when hovered.
`hoverBorderWidth`	arc border width when hovered (in pixels).

All these values, if undefined, fallback to the associated elements.arc.* options.

Config Options

These are the customisation options specific to Polar Area charts. These options are merged with the global chart default options, and form the options of the chart.

Name	Type	Default	Description
`startAngle`	`number`	`-0.5 * Math.PI`	Starting angle to draw arcs for the first item in a dataset.
`animation.animateRotate`	`boolean`	`true`	If true, the chart will animate in with a rotation animation. This property is in the `options.animation` object.
`animation.animateScale`	`boolean`	`true`	If true, will animate scaling the chart from the center outwards.

Default Options

We can also change these defaults values for each PolarArea type that is created, this object is available at Chart.defaults.polarArea. Changing the global options only affects charts created after the change. Existing charts are not changed.

For example, to configure all new polar area charts with animateScale = false you would do:

Chart.defaults.polarArea.animation.animateScale = false;

Data Structure

For a polar area chart, datasets need to contain an array of data points. The data points should be a number, Chart.js will total all of the numbers and calculate the relative proportion of each.

You also need to specify an array of labels so that tooltips appear correctly for each slice.

data = {
    datasets: [{
        data: [10, 20, 30]
    }],
    // These labels appear in the legend and in the tooltips when hovering different arcs
    labels: [
        'Red',
        'Yellow',
        'Blue'
    ]
};