Chart.js/docs/axes/radial/linear.md

Linear Radial Axis

The linear radial scale is used to chart numerical data. As the name suggests, linear interpolation is used to determine where a value lies in relation to the center of the axis.

The following additional configuration options are provided by the radial linear scale.

Configuration Options

Linear Radial Axis specific options

Namespace: options.scales[scaleId]

Name	Type	Default	Description
animate	boolean	true	Whether to animate scaling the chart from the centre
angleLines	object		Angle line configuration. more...
beginAtZero	boolean	false	if true, scale will include 0 if it is not already included.
pointLabels	object		Point label configuration. more...
startAngle	number	0	Starting angle of the scale. In degrees, 0 is at top.

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Tick Configuration

Linear Radial Axis specific tick options

Namespace: options.scales[scaleId].ticks

Name	Type	Scriptable	Default	Description
backdropColor	Color	Yes	'rgba(255, 255, 255, 0.75)'	Color of label backdrops.
backdropPadding	Padding	Yes	2	Padding of label backdrop.
count	number	Yes	undefined	The number of ticks to generate. If specified, this overrides the automatic generation.
format	object	Yes		The Intl.NumberFormat options used by the default label formatter
maxTicksLimit	number	Yes	11	Maximum number of ticks and gridlines to show.
precision	number	Yes		if defined and stepSize is not specified, the step size will be rounded to this many decimal places.
stepSize	number	Yes		User defined fixed step size for the scale. more...
showLabelBackdrop	boolean	Yes	true	If true, draw a background behind the tick labels.

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The scriptable context is described in Options section.

Axis Range Settings

Given the number of axis range settings, it is important to understand how they all interact with each other.

The suggestedMax and suggestedMin settings only change the data values that are used to scale the axis. These are useful for extending the range of the axis while maintaining the auto fit behaviour.

let minDataValue = Math.min(mostNegativeValue, options.ticks.suggestedMin);
let maxDataValue = Math.max(mostPositiveValue, options.ticks.suggestedMax);

In this example, the largest positive value is 50, but the data maximum is expanded out to 100. However, because the lowest data value is below the suggestedMin setting, it is ignored.

let chart = new Chart(ctx, {
    type: 'radar',
    data: {
        datasets: [{
            label: 'First dataset',
            data: [0, 20, 40, 50]
        }],
        labels: ['January', 'February', 'March', 'April']
    },
    options: {
        scales: {
            r: {
                suggestedMin: 50,
                suggestedMax: 100
            }
        }
    }
});

In contrast to the suggested* settings, the min and max settings set explicit ends to the axes. When these are set, some data points may not be visible.

Step Size

If set, the scale ticks will be enumerated by multiple of stepSize, having one tick per increment. If not set, the ticks are labeled automatically using the nice numbers algorithm.

This example sets up a chart with a y axis that creates ticks at 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5.

let options = {
    scales: {
        r: {
            max: 5,
            min: 0,
            ticks: {
                stepSize: 0.5
            }
        }
    }
};

Angle Line Options

The following options are used to configure angled lines that radiate from the center of the chart to the point labels. Namespace: options.scales[scaleId].angleLines

Name	Type	Scriptable	Default	Description
display	boolean		true	if true, angle lines are shown.
color	Color	Yes	Chart.defaults.borderColor	Color of angled lines.
lineWidth	number	Yes	1	Width of angled lines.
borderDash	number[]	Yes1	[]	Length and spacing of dashes on angled lines. See MDN.
borderDashOffset	number	Yes	0.0	Offset for line dashes. See MDN.

1. the borderDash setting only accepts a static value or a function. Passing an array of arrays is not supported.

The scriptable context is described in Options section.

Point Label Options

The following options are used to configure the point labels that are shown on the perimeter of the scale. Namespace: options.scales[scaleId].pointLabels

Name	Type	Scriptable	Default	Description
backdropColor	Color	true	undefined	Background color of the point label.
backdropPadding	Padding		2	Padding of label backdrop.
display	boolean		true	if true, point labels are shown.
callback	function			Callback function to transform data labels to point labels. The default implementation simply returns the current string.
color	Color	Yes	Chart.defaults.color	Color of label.
font	Font	Yes	Chart.defaults.font	See Fonts
padding	number	Yes	5	Padding between chart and point labels.

The scriptable context is described in Options section.

Internal data format

Internally, the linear radial scale uses numeric data