137 lines
5.4 KiB
Markdown
137 lines
5.4 KiB
Markdown
# Doughnut and Pie
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Pie and doughnut charts are probably the most commonly used charts. They are divided into segments, the arc of each segment shows the proportional value of each piece of data.
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They are excellent at showing the relational proportions between data.
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Pie and doughnut charts are effectively the same class in Chart.js, but have one different default value - their `cutoutPercentage`. This equates what percentage of the inner should be cut out. This defaults to `0` for pie charts, and `50` for doughnuts.
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They are also registered under two aliases in the `Chart` core. Other than their different default value, and different alias, they are exactly the same.
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{% chartjs %}
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{
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"type": "doughnut",
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"data": {
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"labels": [
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"Red",
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"Blue",
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"Yellow"
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],
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"datasets": [{
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"label": "My First Dataset",
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"data": [300, 50, 100],
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"backgroundColor": [
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"rgb(255, 99, 132)",
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"rgb(54, 162, 235)",
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"rgb(255, 205, 86)"
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]
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}]
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}
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}
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{% endchartjs %}
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## Example Usage
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```javascript
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// For a pie chart
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var myPieChart = new Chart(ctx, {
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type: 'pie',
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data: data,
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options: options
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});
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```
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```javascript
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// And for a doughnut chart
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var myDoughnutChart = new Chart(ctx, {
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type: 'doughnut',
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data: data,
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options: options
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});
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```
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## Dataset Properties
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The doughnut/pie chart allows a number of properties to be specified for each dataset. These are used to set display properties for a specific dataset. For example, the colour of a the dataset's arc are generally set this way.
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| Name | Type | [Scriptable](../general/options.md#scriptable-options) | [Indexable](../general/options.md#indexable-options) | Default
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| ---- | ---- | :----: | :----: | ----
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| [`backgroundColor`](#styling) | [`Color`](../general/colors.md) | Yes | Yes | `'rgba(0, 0, 0, 0.1)'`
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| [`borderAlign`](#border-alignment) | `string` | Yes | Yes | `'center'`
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| [`borderColor`](#styling) | [`Color`](../general/colors.md) | Yes | Yes | `'#fff'`
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| [`borderWidth`](#styling) | `number` | Yes | Yes | `2`
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| [`data`](#data-structure) | `number[]` | - | - | **required**
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| [`hoverBackgroundColor`](#interations) | [`Color`](../general/colors.md) | Yes | Yes | `undefined`
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| [`hoverBorderColor`](#interactions) | [`Color`](../general/colors.md) | Yes | Yes | `undefined`
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| [`hoverBorderWidth`](#interactions) | `number` | Yes | Yes | `undefined`
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| [`weight`](#styling) | `number` | - | - | `1`
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### Styling
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The style of each arc can be controlled with the following properties:
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| Name | Description
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| ---- | ----
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| `backgroundColor` | arc background color.
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| `borderColor` | arc border color.
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| `borderWidth` | arc border width (in pixels).
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| `weight` | The relative thickness of the dataset. Providing a value for weight will cause the pie or doughnut dataset to be drawn with a thickness relative to the sum of all the dataset weight values.
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All these values, if `undefined`, fallback to the associated [`elements.arc.*`](../configuration/elements.md#arc-configuration) options.
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### Border Alignment
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The following values are supported for `borderAlign`.
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* `'center'` (default)
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* `'inner'`
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When `'center'` is set, the borders of arcs next to each other will overlap. When `'inner'` is set, it is guaranteed that all the borders are not overlap.
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### Interactions
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The interaction with each arc can be controlled with the following properties:
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| Name | Description
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| ---- | -----------
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| `hoverBackgroundColor` | arc background color when hovered.
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| `hoverBorderColor` | arc border color when hovered.
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| `hoverBorderWidth` | arc border width when hovered (in pixels).
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All these values, if `undefined`, fallback to the associated [`elements.arc.*`](../configuration/elements.md#arc-configuration) options.
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## Config Options
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These are the customisation options specific to Pie & Doughnut charts. These options are merged with the global chart configuration options, and form the options of the chart.
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| Name | Type | Default | Description
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| ---- | ---- | ------- | -----------
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| `cutoutPercentage` | `number` | `50` - for doughnut, `0` - for pie | The percentage of the chart that is cut out of the middle.
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| `rotation` | `number` | `-0.5 * Math.PI` | Starting angle to draw arcs from.
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| `circumference` | `number` | `2 * Math.PI` | Sweep to allow arcs to cover.
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| `animation.animateRotate` | `boolean` | `true` | If true, the chart will animate in with a rotation animation. This property is in the `options.animation` object.
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| `animation.animateScale` | `boolean` | `false` | If true, will animate scaling the chart from the center outwards.
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## Default Options
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We can also change these default values for each Doughnut type that is created, this object is available at `Chart.defaults.doughnut`. Pie charts also have a clone of these defaults available to change at `Chart.defaults.pie`, with the only difference being `cutoutPercentage` being set to 0.
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## Data Structure
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For a pie chart, datasets need to contain an array of data points. The data points should be a number, Chart.js will total all of the numbers and calculate the relative proportion of each.
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You also need to specify an array of labels so that tooltips appear correctly.
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```javascript
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data = {
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datasets: [{
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data: [10, 20, 30]
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}],
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// These labels appear in the legend and in the tooltips when hovering different arcs
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labels: [
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'Red',
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'Yellow',
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'Blue'
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]
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};
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```
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