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92 lines
3.0 KiB
Markdown
92 lines
3.0 KiB
Markdown
---
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title: Polar Area Chart
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anchor: polar-area-chart
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---
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### Introduction
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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.
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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.
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<div class="canvas-holder">
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<canvas width="250" height="125"></canvas>
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</div>
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### Example usage
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```javascript
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new Chart(ctx, {
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data: data,
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type: 'polarArea',
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options: options
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});
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```
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### Data structure
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```javascript
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var data = {
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datasets: [{
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data: [
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10,
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32,
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53,
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14,
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22,
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],
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backgroundColor: [
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"#F7464A",
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"#46BFBD",
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"#FDB45C",
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"#949FB1",
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"#4D5360",
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],
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label: 'My dataset' // for legend
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}],
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labels: [
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"Red",
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"Green",
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"Yellow",
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"Grey",
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"Dark Grey"
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]
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};
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```
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As you can see, for the chart data you pass in an array of objects, with a value and a colour. The value attribute should be a number, while the color attribute should be a string. Similar to CSS, for this string you can use HEX notation, RGB, RGBA or HSL.
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### Chart options
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These are the customisation options specific to Polar Area charts. These options are merged with the [global chart configuration options](#getting-started-global-chart-configuration), and form the options of the chart.
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Name | Type | Default | Description
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--- | --- | --- | ---
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scale | Array | [See Scales](#scales) and [Defaults for Radial Linear Scale](#getting-started-radial-linear-scale) | Options for the one scale used on the chart. Use this to style the ticks, labels, and grid.
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*scale*.type | String |"radialLinear" | As defined in ["Radial Linear"](#scales-radial-linear-scale).
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*scale*.lineArc | Boolean | true | When true, lines are circular.
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animateRotate | Boolean |true | If true, will animate the rotation of the chart.
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animateScale | Boolean | true | If true, will animate scaling the chart.
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*legend*.*labels*.generateLabels | Function | `function(data) {} ` | Returns labels for each the legend
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*legend*.onClick | Function | function(event, legendItem) {} ` | Handles clicking an individual legend item
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legendCallback | Function | `function(chart) ` | Generates the HTML legend via calls to `generateLegend`
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You can override these for your `Chart` instance by passing a second argument into the `PolarArea` method as an object with the keys you want to override.
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For example, we could have a polar area chart with a black stroke on each segment like so:
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```javascript
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new Chart(ctx, {
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data: data,
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type: "polarArea",
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options: {
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elements: {
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arc: {
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borderColor: "#000000"
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}
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}
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}
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});
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// This will create a chart with all of the default options, merged from the global config,
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// and the PolarArea chart defaults but this particular instance will have `elements.arc.borderColor` set to `"#000000"`.
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```
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We can also change these defaults values for each PolarArea type that is created, this object is available at `Chart.defaults.polarArea`.
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