# Linear Axis

The linear scale is used to chart numerical data. It can be placed on either the x or y-axis. The scatter chart type automatically configures a line chart to use one of these scales for the x-axis. As the name suggests, linear interpolation is used to determine where a value lies on the axis.

# Configuration Options

# Linear Axis specific options

Namespace: options.scales[scaleId]

Name Type Description
beginAtZero boolean if true, scale will include 0 if it is not already included.
grace number|string Percentage (string ending with %) or amount (number) for added room in the scale range above and below data. more...

# Common options to all cartesian axes

Namespace: options.scales[scaleId]

Name Type Default Description
bounds string 'ticks' Determines the scale bounds. more...
position string | object Position of the axis. more...
stack string Stack group. Axes at the same position with same stack are stacked.
stackWeight number 1 Weight of the scale in stack group. Used to determine the amount of allocated space for the scale within the group.
axis string Which type of axis this is. Possible values are: 'x', 'y'. If not set, this is inferred from the first character of the ID which should be 'x' or 'y'.
offset boolean false If true, extra space is added to the both edges and the axis is scaled to fit into the chart area. This is set to true for a bar chart by default.
title object Scale title configuration. more...

# 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 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 cartesian axes

Namespace: options.scales[scaleId].ticks

Name Type Default Description
align string 'center' The tick alignment along the axis. Can be 'start', 'center', or 'end'.
crossAlign string 'near' The tick alignment perpendicular to the axis. Can be 'near', 'center', or 'far'. See Tick Alignment
sampleSize number ticks.length The number of ticks to examine when deciding how many labels will fit. Setting a smaller value will be faster, but may be less accurate when there is large variability in label length.
autoSkip boolean true If true, automatically calculates how many labels can be shown and hides labels accordingly. Labels will be rotated up to maxRotation before skipping any. Turn autoSkip off to show all labels no matter what.
autoSkipPadding number 3 Padding between the ticks on the horizontal axis when autoSkip is enabled.
includeBounds boolean true Should the defined min and max values be presented as ticks even if they are not "nice".
labelOffset number 0 Distance in pixels to offset the label from the centre point of the tick (in the x-direction for the x-axis, and the y-direction for the y-axis). Note: this can cause labels at the edges to be cropped by the edge of the canvas
maxRotation number 50 Maximum rotation for tick labels when rotating to condense labels. Note: Rotation doesn't occur until necessary. Note: Only applicable to horizontal scales.
minRotation number 0 Minimum rotation for tick labels. Note: Only applicable to horizontal scales.
mirror boolean false Flips tick labels around axis, displaying the labels inside the chart instead of outside. Note: Only applicable to vertical scales.
padding number 0 Padding between the tick label and the axis. When set on a vertical axis, this applies in the horizontal (X) direction. When set on a horizontal axis, this applies in the vertical (Y) direction.

# 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.

# 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: {
        y: {
            max: 5,
            min: 0,
            ticks: {
                stepSize: 0.5
            }
        }
    }
};

# Grace

If the value is string ending with %, its treat as percentage. If number, its treat as value. The value is added to the maximum data value and subtracted from the minimum data. This extends the scale range as if the data values were that much greater.

const config = {
  type: 'bar',
  data,
  options: {
    scales: {
      y: {
        type: 'linear',
        grace: '5%'
      }
    },
    plugins: {
      legend: false
    }
  }
};

# Internal data format

Internally, the linear scale uses numeric data

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