Chart.js/docs/04-Radar-Chart.md

title	anchor
Radar Chart	radar-chart

###Introduction A radar chart is a way of showing multiple data points and the variation between them.

They are often useful for comparing the points of two or more different data sets.

###Example usage

var myRadarChart = new Chart(ctx,{
	type:'radar',
	data: data,
	options: options
});

###Data structure

var data = {
	labels: ["Eating", "Drinking", "Sleeping", "Designing", "Coding", "Cycling", "Running"],
	datasets: [
		{
			label: "My First dataset",
			backgroundColor: "rgba(220,220,220,0.2)",
			borderColor: "rgba(220,220,220,1)",
			pointBackgroundColor: "rgba(220,220,220,1)",
			pointBorderColor: "#fff",
			pointHoverBackgroundColor: "#fff",
			pointHoverBorderColor: "rgba(220,220,220,1)",
			data: [65, 59, 90, 81, 56, 55, 40]
		},
		{
			label: "My Second dataset",
			backgroundColor: "rgba(151,187,205,0.2)",
			borderColor: "rgba(151,187,205,1)",
			pointBackgroundColor: "rgba(151,187,205,1)",
			pointBorderColor: "#fff",
			pointHoverBackgroundColor: "#fff",
			pointHoverBorderColor: "rgba(151,187,205,1)",
			data: [28, 48, 40, 19, 96, 27, 100]
		}
	]
};

For a radar chart, to provide context of what each point means, we include an array of strings that show around each point in the chart. For the radar chart data, we have an array of datasets. Each of these is an object, with a fill colour, a stroke colour, a colour for the fill of each point, and a colour for the stroke of each point. We also have an array of data values.

The label key on each dataset is optional, and can be used when generating a scale for the chart.

Chart options

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

The default options for radar chart are defined in Chart.defaults.radar.

Name	Type	Default	Description
scale	Array	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 lines.
scale.type	String	"radialLinear"	As defined in "Radial Linear".
elements.line	Array		Options for all line elements used on the chart, as defined in the global elements, duplicated here to show Radar chart specific defaults.
elements.line.tension	Number	0	Tension exhibited by lines when calculating splineCurve.

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

For example, we could have a radar chart without a point for each on piece of data by doing the following:

new Chart(ctx, {
	type:"radar",
	data: data,
	options: {
			scale: {
				reverse: true,
				ticks: {
					beginAtZero: true
				}
			}
	}
});
// This will create a chart with all of the default options, merged from the global config,
//  and the Radar chart defaults but this particular instance's scale will be reversed as
// well as the ticks beginning at zero.

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

Prototype methods

.getPointsAtEvent( event )

Calling getPointsAtEvent(event) on your Chart instance passing an argument of an event, or jQuery event, will return the point elements that are at that the same position of that event.

canvas.onclick = function(evt){
	var activePoints = myRadarChart.getPointsAtEvent(evt);
	// => activePoints is an array of points on the canvas that are at the same position as the click event.
};

This functionality may be useful for implementing DOM based tooltips, or triggering custom behaviour in your application.

.update( )

Calling update() on your Chart instance will re-render the chart with any updated values, allowing you to edit the value of multiple existing points, then render those in one animated render loop.

myRadarChart.datasets[0].points[2].value = 50;
// Would update the first dataset's value of 'Sleeping' to be 50
myRadarChart.update();
// Calling update now animates the position of Sleeping from 90 to 50.

.addData( valuesArray, label )

Calling addData(valuesArray, label) on your Chart instance passing an array of values for each dataset, along with a label for those points.

// The values array passed into addData should be one for each dataset in the chart
myRadarChart.addData([40, 60], "Dancing");
// The new data will now animate at the end of the chart.

.removeData( )

Calling removeData() on your Chart instance will remove the first value for all datasets on the chart.

myRadarChart.removeData();
// Other points will now animate to their correct positions.