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* Initial work * Update doc commands * Updated sidebar config * Move docs * Update theme version and enable * Convert to chart.js sample * Update scripts to point to local build * Chart.js from local build * Simplify getting-started example * Axis docs updated except for imported content * Common ticks import works * Chart type docs ported to editor plugin * Last pages to use editor * Fix small errors * Frontmatter title to heading * Remove duplicate example * Update sidebar * Add paths * Remove paths * Add getting-started back * Update menus and add copyright to license section of the docs * Add GA plugin * Style sub-groups * Remove unneeded license page since it is covered on the main page * Remove docusaurus readme page * Remove docusaurus files * Fix issues in docs * Build and deploy scripts for docs work * Conditional base URL for nice local testing * Use eslint-plugin-markdown * Remove hard coded lines * Remove mentions of docusaurus Co-authored-by: Jukka Kurkela <jukka.kurkela@gmail.com>
99 lines
4.7 KiB
Markdown
99 lines
4.7 KiB
Markdown
# Axes
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Axes are an integral part of a chart. They are used to determine how data maps to a pixel value on the chart. In a cartesian chart, there is 1 or more X-axis and 1 or more Y-axis to map points onto the 2-dimensional canvas. These axes are known as ['cartesian axes'](./cartesian/index#cartesian-axes).
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In a radial chart, such as a radar chart or a polar area chart, there is a single axis that maps points in the angular and radial directions. These are known as ['radial axes'](./radial/index#radial-axes).
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Scales in Chart.js >v2.0 are significantly more powerful, but also different than those of v1.0.
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* Multiple X & Y axes are supported.
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* A built-in label auto-skip feature detects would-be overlapping ticks and labels and removes every nth label to keep things displaying normally.
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* Scale titles are supported.
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* New scale types can be extended without writing an entirely new chart type.
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## Common Configuration
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!!!include(axes/_common.md)!!!
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## Tick Configuration
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!!!include(axes/_common_ticks.md)!!!
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## Axis Range Settings
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Given the number of axis range settings, it is important to understand how they all interact with each other.
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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.
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```javascript
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let minDataValue = Math.min(mostNegativeValue, options.suggestedMin);
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let maxDataValue = Math.max(mostPositiveValue, options.suggestedMax);
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```
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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.
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```javascript
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let chart = new Chart(ctx, {
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type: 'line',
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data: {
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datasets: [{
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label: 'First dataset',
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data: [0, 20, 40, 50]
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}],
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labels: ['January', 'February', 'March', 'April']
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},
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options: {
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scales: {
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y: {
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suggestedMin: 50,
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suggestedMax: 100
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}
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}
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}
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});
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```
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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.
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## Stacking
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By default data is not stacked. If the `stacked` option of the value scale (y-axis on horizontal chart) is `true`, positive and negative values are stacked separately. Additionally a `stack` option can be defined per dataset to further divide into stack groups [more...](../general/data-structures/#dataset-configuration).
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For some charts, you might want to stack positive and negative values together. That can be achieved by specifying `stacked: 'single'`.
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## Callbacks
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There are a number of config callbacks that can be used to change parameters in the scale at different points in the update process. The options are supplied at the top level of the axis options.
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Namespace: `options.scales[scaleId]`
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| Name | Arguments | Description
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| ---- | --------- | -----------
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| `beforeUpdate` | `axis` | Callback called before the update process starts.
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| `beforeSetDimensions` | `axis` | Callback that runs before dimensions are set.
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| `afterSetDimensions` | `axis` | Callback that runs after dimensions are set.
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| `beforeDataLimits` | `axis` | Callback that runs before data limits are determined.
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| `afterDataLimits` | `axis` | Callback that runs after data limits are determined.
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| `beforeBuildTicks` | `axis` | Callback that runs before ticks are created.
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| `afterBuildTicks` | `axis` | Callback that runs after ticks are created. Useful for filtering ticks.
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| `beforeTickToLabelConversion` | `axis` | Callback that runs before ticks are converted into strings.
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| `afterTickToLabelConversion` | `axis` | Callback that runs after ticks are converted into strings.
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| `beforeCalculateTickRotation` | `axis` | Callback that runs before tick rotation is determined.
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| `afterCalculateTickRotation` | `axis` | Callback that runs after tick rotation is determined.
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| `beforeFit` | `axis` | Callback that runs before the scale fits to the canvas.
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| `afterFit` | `axis` | Callback that runs after the scale fits to the canvas.
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| `afterUpdate` | `axis` | Callback that runs at the end of the update process.
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### Updating Axis Defaults
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The default configuration for a scale can be easily changed. All you need to do is set the new options to `Chart.defaults.scales[type]`.
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For example, to set the minimum value of 0 for all linear scales, you would do the following. Any linear scales created after this time would now have a minimum of 0.
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```javascript
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Chart.defaults.scales.linear.min = 0;
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```
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## Creating New Axes
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To create a new axis, see the [developer docs](../developers/axes.md).
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