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5.3 KiB
Markdown
109 lines
5.3 KiB
Markdown
# Cartesian Axes
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Axes that follow a cartesian grid are known as 'Cartesian Axes'. Cartesian axes are used for line, bar, and bubble charts. Four cartesian axes are included in Chart.js by default.
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* [linear](./linear.md#linear-cartesian-axis)
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* [logarithmic](./logarithmic.md#logarithmic-cartesian-axis)
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* [category](./category.md#category-cartesian-axis)
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* [time](./time.md#time-cartesian-axis)
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## Common Configuration
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All of the included cartesian axes support a number of common options.
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| Name | Type | Default | Description
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| ---- | ---- | ------- | -----------
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| `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.
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| `position` | `string` | | Position of the axis in the chart. Possible values are: `'top'`, `'left'`, `'bottom'`, `'right'`
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| `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.
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| `id` | `string` | | The ID is used to link datasets and scale axes together. [more...](#axis-id)
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| `gridLines` | `object` | | Grid line configuration. [more...](../styling.md#grid-line-configuration)
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| `scaleLabel` | `object` | | Scale title configuration. [more...](../labelling.md#scale-title-configuration)
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| `ticks` | `object` | | Tick configuration. [more...](#tick-configuration)
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### Tick Configuration
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The following options are common to all cartesian axes but do not apply to other axes.
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| Name | Type | Default | Description
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| ---- | ---- | ------- | -----------
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| `min` | `number` | | User defined minimum value for the scale, overrides minimum value from data.
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| `max` | `number` | | User defined maximum value for the scale, overrides maximum value from data.
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| `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.
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| `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.
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| `autoSkipPadding` | `number` | `0` | Padding between the ticks on the horizontal axis when `autoSkip` is enabled.
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| `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*
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| `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.*
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| `minRotation` | `number` | `0` | Minimum rotation for tick labels. *Note: Only applicable to horizontal scales.*
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| `mirror` | `boolean` | `false` | Flips tick labels around axis, displaying the labels inside the chart instead of outside. *Note: Only applicable to vertical scales.*
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| `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.
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### Axis ID
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The properties `dataset.xAxisID` or `dataset.yAxisID` have to match the scale properties `scales.xAxes.id` or `scales.yAxes.id`. This is especially needed if multi-axes charts are used.
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```javascript
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var myChart = new Chart(ctx, {
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type: 'line',
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data: {
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datasets: [{
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// This dataset appears on the first axis
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yAxisID: 'first-y-axis'
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}, {
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// This dataset appears on the second axis
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yAxisID: 'second-y-axis'
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}]
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},
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options: {
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scales: {
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yAxes: [{
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id: 'first-y-axis',
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type: 'linear'
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}, {
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id: 'second-y-axis',
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type: 'linear'
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}]
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}
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}
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});
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```
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## Creating Multiple Axes
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With cartesian axes, it is possible to create multiple X and Y axes. To do so, you can add multiple configuration objects to the `xAxes` and `yAxes` properties. When adding new axes, it is important to ensure that you specify the type of the new axes as default types are **not** used in this case.
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In the example below, we are creating two Y axes. We then use the `yAxisID` property to map the datasets to their correct axes.
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```javascript
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var myChart = new Chart(ctx, {
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type: 'line',
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data: {
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datasets: [{
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data: [20, 50, 100, 75, 25, 0],
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label: 'Left dataset',
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// This binds the dataset to the left y axis
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yAxisID: 'left-y-axis'
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}, {
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data: [0.1, 0.5, 1.0, 2.0, 1.5, 0],
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label: 'Right dataset',
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// This binds the dataset to the right y axis
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yAxisID: 'right-y-axis'
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}],
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labels: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun']
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},
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options: {
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scales: {
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yAxes: [{
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id: 'left-y-axis',
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type: 'linear',
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position: 'left'
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}, {
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id: 'right-y-axis',
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type: 'linear',
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position: 'right'
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}]
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}
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}
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});
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```
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