# 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.

# Common options to all axes

Namespace: options.scales[scaleId]

Name Type Default Description
type string Type of scale being employed. Custom scales can be created and registered with a string key. This allows changing the type of an axis for a chart.
alignToPixels boolean false Align pixel values to device pixels.
backgroundColor Color Background color of the scale area.
display boolean|string true Controls the axis global visibility (visible when true, hidden when false). When display: 'auto', the axis is visible only if at least one associated dataset is visible.
grid object Grid line configuration. more...
min number User defined minimum number for the scale, overrides minimum value from data. more...
max number User defined maximum number for the scale, overrides maximum value from data. more...
reverse boolean false Reverse the scale.
stacked boolean|string false Should the data be stacked. more...
suggestedMax number Adjustment used when calculating the maximum data value. more...
suggestedMin number Adjustment used when calculating the minimum data value. more...
ticks object Tick configuration. more...
weight number 0 The weight used to sort the axis. Higher weights are further away from the chart area.

# Tick Configuration

# Linear Radial Axis specific tick options

Namespace: options.scales[scaleId].ticks

Name Type Scriptable Default Description
count number Yes undefined The number of ticks to generate. If specified, this overrides the automatic generation.
format object Yes The Intl.NumberFormat (opens new window) 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...

# Common tick options to all axes

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 2 Padding of label backdrop.
callback function Returns the string representation of the tick value as it should be displayed on the chart. See callback.
display boolean true If true, show tick labels.
color Color Yes Chart.defaults.color Color of ticks.
font Font Yes Chart.defaults.font See Fonts
major object {} Major ticks configuration.
padding number 3 Sets the offset of the tick labels from the axis
showLabelBackdrop boolean Yes true for radial scale, false otherwise If true, draw a background behind the tick labels.
textStrokeColor Color Yes `` The color of the stroke around the text.
textStrokeWidth number Yes 0 Stroke width around the text.
z number 0 z-index of tick layer. Useful when ticks are drawn on chart area. Values <= 0 are drawn under datasets, > 0 on top.

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 (opens new window).
borderDashOffset number Yes 0.0 Offset for line dashes. See MDN (opens new window).
  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

Last Updated: 11/30/2021, 6:14:49 PM