File: vendors/chart.js/docs/06-Polar-Area-Chart.md

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title: Polar Area Chart anchor: polar-area-chart

Introduction

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.

<div class="canvas-holder">

<canvas width="250" height="125"></canvas>

</div>

Example Usage

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

Data Structure

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

Some properties are specified as arrays. The first value applies to the first bar, the second value to the second bar, and so on.

Property | Type | Usage --- | --- | --- data | Array<Number> | The data to plot as bars label | String | The label for the dataset which appears in the legend and tooltips backgroundColor | Array<Color> | The fill color of the arcs. See Colors borderColor | Array<Color> | Arc border color borderWidth | Array<Number> | Border width of arcs in pixels hoverBackgroundColor | Array<Color> | Arc background color when hovered hoverBorderColor | Array<Color> | Arc border color when hovered hoverBorderWidth | Array<Number> | Border width of arc when hovered

An example data object using these attributes is shown below.

var data = {
	datasets: [{
		data: [
			11,
			16,
			7,
			3,
			14
		],
		backgroundColor: [
			"#FF6384",
			"#4BC0C0",
			"#FFCE56",
			"#E7E9ED",
			"#36A2EB"
		],
		label: 'My dataset' // for legend
	}],
	labels: [
		"Red",
		"Green",
		"Yellow",
		"Grey",
		"Blue"
	]
};

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.

Chart Options

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

Name | Type | Default | Description --- | --- | --- | --- scale | Object | See Scales and Defaults for Radial Linear Scale | Options for the one scale used on the chart. Use this to style the ticks, labels, and grid. scale.type | String |"radialLinear" | As defined in "Radial Linear". scale.lineArc | Boolean | true | When true, lines are circular. animation.animateRotate | Boolean |true | If true, will animate the rotation of the chart. animation.animateScale | Boolean | true | If true, will animate scaling the chart. legend.labels.generateLabels | Function | function(data) {} | Returns labels for each the legend legend.onClick | Function | function(event, legendItem) {} ` | Handles clicking an individual legend item legendCallback | Function | function(chart) | Generates the HTML legend via calls to generateLegend

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.

For example, we could have a polar area chart with a black stroke on each segment like so:

new Chart(ctx, {
	data: data,
	type: "polarArea",
	options: {
		elements: {
			arc: {
				borderColor: "#000000"
			}
		}
	}
});
// This will create a chart with all of the default options, merged from the global config,
// and the PolarArea chart defaults but this particular instance will have `elements.arc.borderColor` set to `"#000000"`.

We can also change these defaults values for each PolarArea type that is created, this object is available at Chart.defaults.polarArea.


For more information send a message to info at phpclasses dot org.