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94 lines
3.4 KiB
Markdown
94 lines
3.4 KiB
Markdown
---
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title: Radar Chart
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anchor: radar-chart
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---
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### Introduction
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A radar chart is a way of showing multiple data points and the variation between them.
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They are often useful for comparing the points of two or more different data sets.
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<div class="canvas-holder">
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<canvas width="250" height="125"></canvas>
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</div>
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### Example usage
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```javascript
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var myRadarChart = new Chart(ctx, {
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type: 'radar',
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data: data,
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options: options
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});
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```
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### Data structure
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```javascript
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var data = {
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labels: ["Eating", "Drinking", "Sleeping", "Designing", "Coding", "Cycling", "Running"],
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datasets: [
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{
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label: "My First dataset",
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backgroundColor: "rgba(179,181,198,0.2)",
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borderColor: "rgba(179,181,198,1)",
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pointBackgroundColor: "rgba(179,181,198,1)",
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pointBorderColor: "#fff",
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pointHoverBackgroundColor: "#fff",
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pointHoverBorderColor: "rgba(179,181,198,1)",
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data: [65, 59, 90, 81, 56, 55, 40]
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},
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{
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label: "My Second dataset",
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backgroundColor: "rgba(255,99,132,0.2)",
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borderColor: "rgba(255,99,132,1)",
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pointBackgroundColor: "rgba(255,99,132,1)",
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pointBorderColor: "#fff",
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pointHoverBackgroundColor: "#fff",
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pointHoverBorderColor: "rgba(255,99,132,1)",
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data: [28, 48, 40, 19, 96, 27, 100]
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}
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]
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};
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```
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For a radar chart, to provide context of what each point means, we include an array of strings that show around each point in the chart.
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For the radar chart data, we have an array of datasets. Each of these is an object, with a fill colour, a stroke colour, a colour for the fill of each point, and a colour for the stroke of each point. We also have an array of data values.
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The label key on each dataset is optional, and can be used when generating a scale for the chart.
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### Chart Options
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These are the customisation options specific to Radar charts. These options are merged with the [global chart configuration options](#getting-started-global-chart-configuration), and form the options of the chart.
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The default options for radar chart are defined in `Chart.defaults.radar`.
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Name | Type | Default | Description
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--- | --- | --- | ---
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scale | Array | [See Scales](#scales) and [Defaults for Radial Linear Scale](#scales-radial-linear-scale) | Options for the one scale used on the chart. Use this to style the ticks, labels, and grid lines.
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*scale*.type | String |"radialLinear" | As defined in ["Radial Linear"](#scales-radial-linear-scale).
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*elements*.line | Array | | Options for all line elements used on the chart, as defined in the global elements, duplicated here to show Radar chart specific defaults.
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*elements.line*.tension | Number | 0 | Tension exhibited by lines when calculating splineCurve. Setting to 0 creates straight lines.
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You can override these for your `Chart` instance by passing a second argument into the `Radar` method as an object with the keys you want to override.
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For example, we could have a radar chart without a point for each on piece of data by doing the following:
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```javascript
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new Chart(ctx, {
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type: "radar",
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data: data,
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options: {
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scale: {
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reverse: true,
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ticks: {
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beginAtZero: true
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}
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}
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}
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});
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// This will create a chart with all of the default options, merged from the global config,
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// and the Radar chart defaults but this particular instance's scale will be reversed as
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// well as the ticks beginning at zero.
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```
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We can also change these defaults values for each Radar type that is created, this object is available at `Chart.defaults.radar`.
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