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Polar Area Chart

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.

// <block:setup:1>
const data = {
  labels: [
    'Red',
    'Green',
    'Yellow',
    'Grey',
    'Blue'
  ],
  datasets: [{
    label: 'My First Dataset',
    data: [11, 16, 7, 3, 14],
    backgroundColor: [
      'rgb(255, 99, 132)',
      'rgb(75, 192, 192)',
      'rgb(255, 205, 86)',
      'rgb(201, 203, 207)',
      'rgb(54, 162, 235)'
    ]
  }]
};
// </block:setup>

// <block:config:0>
const config = {
  type: 'polarArea',
  data: data,
  options: {}
};
// </block:config>

module.exports = {
  actions: [],
  config: config,
};

Dataset Properties

Namespaces:

  • data.datasets[index] - options for this dataset only
  • options.datasets.polarArea - options for all polarArea datasets
  • options.elements.arc - options for all arc elements
  • options - options for the whole chart

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 'center'|'inner' Yes Yes 'center'
borderColor Color Yes Yes '#fff'
borderJoinStyle 'round'|'bevel'|'miter' Yes Yes undefined
borderWidth number Yes Yes 2
clip number|object|false - - undefined
data number[] - - required
hoverBackgroundColor Color Yes Yes undefined
hoverBorderColor Color Yes Yes undefined
hoverBorderJoinStyle 'round'|'bevel'|'miter' Yes Yes undefined
hoverBorderWidth number Yes Yes undefined
circular boolean Yes Yes true

All these values, if undefined, fallback to the scopes described in option resolution

General

Name Description
clip How to clip relative to chartArea. Positive value allows overflow, negative value clips that many pixels inside chartArea. 0 = clip at chartArea. Clipping can also be configured per side: clip: {left: 5, top: false, right: -2, bottom: 0}

Styling

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

Name Description
backgroundColor arc background color.
borderColor arc border color.
borderJoinStyle arc border join style. See MDN.
borderWidth arc border width (in pixels).
circular By default the Arc is curved. If circular: false the Arc will be flat.

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 do 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.
hoverBorderJoinStyle arc border join style when hovered. See MDN.
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 looked up on access, and form together with the global chart default options the options of the chart.

Name Type Default Description
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.

The polar area chart uses the radialLinear scale. Additional configuration is provided via the scale.

Default Options

We can also change these default values for each PolarArea type that is created, this object is available at Chart.overrides.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.overrides.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'
    ]
};