Category Axis

If the global configuration is used, labels are drawn from one of the label arrays included in the chart data. If only data.labels is defined, this will be used. If data.xLabels is defined and the axis is horizontal, this will be used. Similarly, if data.yLabels is defined and the axis is vertical, this property will be used. Using both xLabels and yLabels together can create a chart that uses strings for both the X and Y axes.

Specifying any of the settings above defines the x-axis as type: 'category' if not defined otherwise. For more fine-grained control of category labels, it is also possible to add labels as part of the category axis definition. Doing so does not apply the global defaults.

Category Axis Definition

Globally:

  1. let chart = new Chart(ctx, {
  2. type: ...
  3. data: {
  4. labels: ['January', 'February', 'March', 'April', 'May', 'June'],
  5. datasets: ...
  6. }
  7. });

As part of axis definition:

  1. let chart = new Chart(ctx, {
  2. type: ...
  3. data: ...
  4. options: {
  5. scales: {
  6. x: {
  7. type: 'category',
  8. labels: ['January', 'February', 'March', 'April', 'May', 'June']
  9. }
  10. }
  11. }
  12. });

Configuration Options

Category Axis specific options

Namespace: options.scales[scaleId]

NameTypeDescription
minstring|numberThe minimum item to display. more…
maxstring|numberThe maximum item to display. more…
labelsstring[]|string[][]An array of labels to display. When an individual label is an array of strings, each item is rendered on a new line.

Common options to all cartesian axes

Namespace: options.scales[scaleId]

NameTypeDefaultDescription
boundsstring‘ticks’Determines the scale bounds. more…
positionstring | objectPosition of the axis. more…
stackstringStack group. Axes at the same position with same stack are stacked.
stackWeightnumber1Weight of the scale in stack group. Used to determine the amount of allocated space for the scale within the group.
axisstringWhich 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’.
offsetbooleanfalseIf 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.
titleobjectScale title configuration. more…

Common options to all axes

Namespace: options.scales[scaleId]

NameTypeDefaultDescription
typestringType 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.
alignToPixelsbooleanfalseAlign pixel values to device pixels.
backgroundColorColorBackground color of the scale area.
displayboolean|stringtrueControls 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.
gridobjectGrid line configuration. more…
minnumberUser defined minimum number for the scale, overrides minimum value from data. more…
maxnumberUser defined maximum number for the scale, overrides maximum value from data. more…
reversebooleanfalseReverse the scale.
stackedboolean|stringfalseShould the data be stacked. more…
suggestedMaxnumberAdjustment used when calculating the maximum data value. more…
suggestedMinnumberAdjustment used when calculating the minimum data value. more…
ticksobjectTick configuration. more…
weightnumber0The weight used to sort the axis. Higher weights are further away from the chart area.

Tick Configuration

Common tick options to all cartesian axes

Namespace: options.scales[scaleId].ticks

NameTypeDefaultDescription
alignstring‘center’The tick alignment along the axis. Can be ‘start’, ‘center’, ‘end’, or ‘inner’. inner alignment means align start for first tick and end for the last tick of horizontal axis
crossAlignstring‘near’The tick alignment perpendicular to the axis. Can be ‘near’, ‘center’, or ‘far’. See Tick Alignment
sampleSizenumberticks.lengthThe 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.
autoSkipbooleantrueIf 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.
autoSkipPaddingnumber3Padding between the ticks on the horizontal axis when autoSkip is enabled.
includeBoundsbooleantrueShould the defined min and max values be presented as ticks even if they are not “nice”.
labelOffsetnumber0Distance 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
maxRotationnumber50Maximum rotation for tick labels when rotating to condense labels. Note: Rotation doesn’t occur until necessary. Note: Only applicable to horizontal scales.
minRotationnumber0Minimum rotation for tick labels. Note: Only applicable to horizontal scales.
mirrorbooleanfalseFlips tick labels around axis, displaying the labels inside the chart instead of outside. Note: Only applicable to vertical scales.
paddingnumber0Padding 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.
maxTicksLimitnumber11Maximum number of ticks and gridlines to show.

Common tick options to all axes

Namespace: options.scales[scaleId].ticks

NameTypeScriptableDefaultDescription
backdropColorColorYes‘rgba(255, 255, 255, 0.75)’Color of label backdrops.
backdropPaddingPadding2Padding of label backdrop.
callbackfunctionReturns the string representation of the tick value as it should be displayed on the chart. See callback.
displaybooleantrueIf true, show tick labels.
colorColorYesChart.defaults.colorColor of ticks.
fontFontYesChart.defaults.fontSee Fonts
majorobject{}Major ticks configuration.
paddingnumber3Sets the offset of the tick labels from the axis
showLabelBackdropbooleanYestrue for radial scale, false otherwiseIf true, draw a background behind the tick labels.
textStrokeColorColorYes``The color of the stroke around the text.
textStrokeWidthnumberYes0Stroke width around the text.
znumber0z-index of tick layer. Useful when ticks are drawn on chart area. Values <= 0 are drawn under datasets, > 0 on top.

Min Max Configuration

For both the min and max properties, the value must be string in the labels array or numeric value as an index of a label in that array. In the example below, the x axis would only display “March” through “June”.

  1. let chart = new Chart(ctx, {
  2. type: 'line',
  3. data: {
  4. datasets: [{
  5. data: [10, 20, 30, 40, 50, 60]
  6. }],
  7. labels: ['January', 'February', 'March', 'April', 'May', 'June']
  8. },
  9. options: {
  10. scales: {
  11. x: {
  12. min: 'March'
  13. }
  14. }
  15. }
  16. });

Internal data format

Internally category scale uses label indices