Opendistrib/vendor/bower/chartjs/docs/07-Pie-Doughnut-Chart.md

---

title: Pie & Doughnut Charts

anchor: doughnut-pie-chart

Introduction

Pie and doughnut charts are probably the most commonly used chart there are. They are divided into segments, the arc of each segment shows the proportional value of each piece of data.

They are excellent at showing the relational proportions between data.

Pie and doughnut charts are effectively the same class in Chart.js, but have one different default value - their cutoutPercentage. This equates what percentage of the inner should be cut out. This defaults to 0 for pie charts, and 50 for doughnuts.

They are also registered under two aliases in the Chart core. Other than their different default value, and different alias, they are exactly the same.

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

Example Usage

// For a pie chart
var myPieChart = new Chart(ctx,{
	type: 'pie',
	data: data,
	options: options
});

// And for a doughnut chart
var myDoughnutChart = new Chart(ctx, {
	type: 'doughnut',
	data: data,
	options: options
});

Data Structure

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 = {
    labels: [
        "Red",
        "Blue",
        "Yellow"
    ],
    datasets: [
        {
            data: [300, 50, 100],
            backgroundColor: [
                "#FF6384",
                "#36A2EB",
                "#FFCE56"
            ],
            hoverBackgroundColor: [
                "#FF6384",
                "#36A2EB",
                "#FFCE56"
            ]
        }]
};

For a pie 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 can also add an array of background colors. The color attributes 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 Pie & Doughnut charts. These options are merged with the global chart configuration options, and form the options of the chart.

Name	Type	Default	Description
cutoutPercentage	Number	50 - for doughnut, 0 - for pie	The percentage of the chart that is cut out of the middle.
rotation	Number	-0.5 * Math.PI	Starting angle to draw arcs from
circumference	Number	2 * Math.PI	Sweep to allow arcs to cover
animation.animateRotate	Boolean	true	If true, will animate the rotation of the chart.
animation.animateScale	Boolean	false	If true, will animate scaling the Doughnut from the centre.
legend.labels.generateLabels	Function	function(chart) {}	Returns a label for each item to be displayed on the legend.
legend.onClick	Function	function(event, legendItem) {} `	Handles clicking an individual legend item

You can override these for your Chart instance by passing a second argument into the Doughnut method as an object with the keys you want to override.

For example, we could have a doughnut chart that animates by scaling out from the centre like so:

new Chart(ctx,{
	type:"doughnut",
	animation:{
		animateScale:true
	}
});
// This will create a chart with all of the default options, merged from the global config,
// and the Doughnut chart defaults but this particular instance will have `animateScale` set to `true`.

We can also change these default values for each Doughnut type that is created, this object is available at Chart.defaults.doughnut. Pie charts also have a clone of these defaults available to change at Chart.defaults.pie, with the only difference being cutoutPercentage being set to 0.