Chart.js

API Documentation

Getting started

Download Chart.js

To download a zip, go to Chart.js on Github and choose the version that is right for your application.

To install via npm / bower:

npm install chart.js --save
bower install Chart.js --save

Selecting the Correct Build

Chart.js provides two different builds that are available for your use. The Chart.js and Chart.min.js files include Chart.js and the accompanying color parsing library. If this version is used and you require the use of the time axis, Moment.js will need to be included before Chart.js.

The Chart.bundle.js and Chart.bundle.min.js builds include Moment.js in a single file. This version should be used if you require time axes and want a single file to include, select this version. Do not use this build if your application already includes Moment.js. If you do, Moment.js will be included twice, increasing the page load time and potentially introducing version issues.

Installation

To import Chart.js using an old-school script tag:

<script src="Chart.js"></script>
<script>
    var myChart = new Chart({...})
</script>

To import Chart.js using an awesome module loader:


// Using CommonJS
var Chart = require('src/chart.js')
var myChart = new Chart({...})

// ES6
import Chart from 'src/chart.js'
let myChart = new Chart({...})

// Using requirejs
require(['path/to/Chartjs'], function(Chart){
 var myChart = new Chart({...})
})

Creating a Chart

To create a chart, we need to instantiate the Chart class. To do this, we need to pass in the node, jQuery instance, or 2d context of the canvas of where we want to draw the chart. Here's an example.

<canvas id="myChart" width="400" height="400"></canvas>
// Any of the following formats may be used
var ctx = document.getElementById("myChart");
var ctx = document.getElementById("myChart").getContext("2d");
var ctx = $("#myChart");

Once you have the element or context, you're ready to instantiate a pre-defined chart-type or create your own!

The following example instantiates a bar chart showing the number of votes for different colors and the y-axis starting at 0.

<canvas id="myChart" width="400" height="400"></canvas>
<script>
var ctx = document.getElementById("myChart");
var myChart = new Chart(ctx, {
    type: 'bar',
    data: {
        labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
        datasets: [{
            label: '# of Votes',
            data: [12, 19, 3, 5, 2, 3],
            backgroundColor: [
                'rgba(255, 99, 132, 0.2)',
                'rgba(54, 162, 235, 0.2)',
                'rgba(255, 206, 86, 0.2)',
                'rgba(75, 192, 192, 0.2)',
                'rgba(153, 102, 255, 0.2)',
                'rgba(255, 159, 64, 0.2)'
            ],
            borderColor: [
                'rgba(255,99,132,1)',
                'rgba(54, 162, 235, 1)',
                'rgba(255, 206, 86, 1)',
                'rgba(75, 192, 192, 1)',
                'rgba(153, 102, 255, 1)',
                'rgba(255, 159, 64, 1)'
            ],
            borderWidth: 1
        }]
    },
    options: {
        scales: {
            yAxes: [{
                ticks: {
                    beginAtZero:true
                }
            }]
        }
    }
});
</script>

It's that easy to get started using Chart.js! From here you can explore the many options that can help you customise your charts with scales, tooltips, labels, colors, custom actions, and much more.

Chart Configuration

Chart.js provides a number of options for changing the behaviour of created charts. These configuration options can be changed on a per chart basis by passing in an options object when creating the chart. Alternatively, the global configuration can be changed which will be used by all charts created after that point.

Creating a Chart with Options

To create a chart with configuration options, simply pass an object containing your configuration to the constructor. In the example below, a line chart is created and configured to not be responsive.

var chartInstance = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        responsive: false
    }
});

Global Configuration

This concept was introduced in Chart.js 1.0 to keep configuration DRY, and allow for changing options globally across chart types, avoiding the need to specify options for each instance, or the default for a particular chart type.

Chart.js merges the options object passed to the chart with the global configuration using chart type defaults and scales defaults appropriately. This way you can be as specific as you would like in your individual chart configuration, while still changing the defaults for all chart types where applicable. The global general options are defined in Chart.defaults.global. The defaults for each chart type are discussed in the documentation for that chart type.

The following example would set the hover mode to 'single' for all charts where this was not overridden by the chart type defaults or the options passed to the constructor on creation.

Chart.defaults.global.hover.mode = 'single';

// Hover mode is set to single because it was not overridden here
var chartInstanceHoverModeSingle = new Chart(ctx, {
    type: 'line',
    data: data,
});

// This chart would have the hover mode that was passed in
var chartInstanceDifferentHoverMode = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        hover: {
            // Overrides the global setting
            mode: 'label'
        }
    }
})

Global Font Settings

There are 4 special global settings that can change all of the fonts on the chart. These options are in Chart.defaults.global.

Name Type Default Description
defaultFontColor Color '#666' Default font color for all text
defaultFontFamily String "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif" Default font family for all text
defaultFontSize Number 12 Default font size (in px) for text. Does not apply to radialLinear scale point labels
defaultFontStyle String 'normal' Default font style. Does not apply to tooltip title or footer. Does not apply to chart title

Common Chart Configuration

The following options are applicable to all charts. The can be set on the global configuration, or they can be passed to the chart constructor.

Name Type Default Description
responsive Boolean true Resizes when the canvas container does.
responsiveAnimationDuration Number 0 Duration in milliseconds it takes to animate to new size after a resize event.
maintainAspectRatio Boolean true Maintain the original canvas aspect ratio (width / height) when resizing
events Array[String] ["mousemove", "mouseout", "click", "touchstart", "touchmove", "touchend"] Events that the chart should listen to for tooltips and hovering
onClick Function null Called if the event is of type 'mouseup' or 'click'. Called in the context of the chart and passed an array of active elements
legendCallback Function function (chart) { } Function to generate a legend. Receives the chart object to generate a legend from. Default implementation returns an HTML string.

Title Configuration

The title configuration is passed into the options.title namespace. The global options for the chart title is defined in Chart.defaults.global.title.

Name Type Default Description
display Boolean false Display the title block
position String 'top' Position of the title. Only 'top' or 'bottom' are currently allowed
fullWidth Boolean true Marks that this box should take the full width of the canvas (pushing down other boxes)
fontSize Number 12 Font size inherited from global configuration
fontFamily String "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif" Font family inherited from global configuration
fontColor Color "#666" Font color inherited from global configuration
fontStyle String 'bold' Font styling of the title.
padding Number 10 Number of pixels to add above and below the title text
text String '' Title text

Example Usage

The example below would enable a title of 'Custom Chart Title' on the chart that is created.

var chartInstance = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        title: {
            display: true,
            text: 'Custom Chart Title'
        }
    }
})

Legend Configuration

The legend configuration is passed into the options.legend namespace. The global options for the chart legend is defined in Chart.defaults.global.legend.

Name Type Default Description
display Boolean true Is the legend displayed
position String 'top' Position of the legend. Options are 'top' or 'bottom'
fullWidth Boolean true Marks that this box should take the full width of the canvas (pushing down other boxes)
onClick Function function(event, legendItem) {} A callback that is called when a click is registered on top of a label item
labels Object - See the Legend Label Configuration section below.

Legend Label Configuration

The legend label configuration is nested below the legend configuration using the labels key.

Name Type Default Description
boxWidth Number 40 Width of coloured box
fontSize Number 12 Font size inherited from global configuration
fontStyle String "normal" Font style inherited from global configuration
fontColor Color "#666" Font color inherited from global configuration
fontFamily String "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif" Font family inherited from global configuration
padding Number 10 Padding between rows of colored boxes
generateLabels: Function function(chart) { } Generates legend items for each thing in the legend. Default implementation returns the text + styling for the color box. See Legend Item for details.

Legend Item Interface

Items passed to the legend onClick function are the ones returned from labels.generateLabels. These items must implement the following interface.

{
    // Label that will be displayed
    text: String,

    // Fill style of the legend box
    fillStyle: Color,

    // If true, this item represents a hidden dataset. Label will be rendered with a strike-through effect
    hidden: Boolean,

    // For box border. See https://developer.mozilla.org/en/docs/Web/API/CanvasRenderingContext2D/lineCap
    lineCap: String,

    // For box border. See https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/setLineDash
    lineDash: Array[Number],

    // For box border. See https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/lineDashOffset
    lineDashOffset: Number,

    // For box border. See https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/lineJoin
    lineJoin: String,

    // Width of box border 
    lineWidth: Number,

    // Stroke style of the legend box
    strokeStyle: Color
}

Example

The following example will create a chart with the legend enabled and turn all of the text red in color.

var chartInstance = new Chart(ctx, {
    type: 'bar',
    data: data,
    options: {
        legend: {
            display: true,
            labels: {
                fontColor: 'rgb(255, 99, 132)'
            }
        }
    }
});

Tooltip Configuration

The title configuration is passed into the options.tooltips namespace. The global options for the chart tooltips is defined in Chart.defaults.global.title.

Name Type Default Description
enabled Boolean true Are tooltips
custom Function null See section below
mode String 'single' Sets which elements appear in the tooltip. Acceptable options are 'single' or 'label'. single highlights the closest element. label highlights elements in all datasets at the same X value.
backgroundColor Color 'rgba(0,0,0,0.8)' Background color of the tooltip
titleFontFamily String "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif" Font family for tooltip title inherited from global font family
titleFontSize Number 12 Font size for tooltip title inherited from global font size
titleFontStyle String "bold"
titleFontColor Color "#fff" Font color for tooltip title
titleSpacing Number 2 Spacing to add to top and bottom of each title line.
titleMarginBottom Number 6 Margin to add on bottom of title section
bodyFontFamily String "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif" Font family for tooltip items inherited from global font family
bodyFontSize Number 12 Font size for tooltip items inherited from global font size
bodyFontStyle String "normal"
bodyFontColor Color "#fff" Font color for tooltip items.
bodySpacing Number 2 Spacing to add to top and bottom of each tooltip item
footerFontFamily String "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif" Font family for tooltip footer inherited from global font family.
footerFontSize Number 12 Font size for tooltip footer inherited from global font size.
footerFontStyle String "bold" Font style for tooltip footer.
footerFontColor Color "#fff" Font color for tooltip footer.
footerSpacing Number 2 Spacing to add to top and bottom of each footer line.
footerMarginTop Number 6 Margin to add before drawing the footer
xPadding Number 6 Padding to add on left and right of tooltip
yPadding Number 6 Padding to add on top and bottom of tooltip
caretSize Number 5 Size, in px, of the tooltip arrow
cornerRadius Number 6 Radius of tooltip corner curves
multiKeyBackground Color "#fff" Color to draw behind the colored boxes when multiple items are in the tooltip
callbacks Object See the callbacks section below

Tooltip Callbacks

The tooltip label configuration is nested below the tooltip configuration using the callbacks key. The tooltip has the following callbacks for providing text. For all functions, 'this' will be the tooltip object created from the Chart.Tooltip constructor.

All functions are called with the same arguments: a tooltip item and the data object passed to the chart. All functions must return either a string or an array of strings. Arrays of strings are treated as multiple lines of text.

Callback Arguments Description
beforeTitle Array[tooltipItem], data Text to render before the title
title Array[tooltipItem], data Text to render as the title
afterTitle Array[tooltipItem], data Text to render after the title
beforeBody Array[tooltipItem], data Text to render before the body section
beforeLabel tooltipItem, data Text to render before an individual label
label tooltipItem, data Text to render for an individual item in the tooltip
afterLabel tooltipItem, data Text to render after an individual label
afterBody Array[tooltipItem], data Text to render after the body section
beforeFooter Array[tooltipItem], data Text to render before the footer section
footer Array[tooltipItem], data Text to render as the footer
afterFooter Array[tooltipItem], data Text to render after the footer section

Tooltip Item Interface

The tooltip items passed to the tooltip callbacks implement the following interface.

{
    // X Value of the tooltip as a string
    xLabel: String,

    // Y value of the tooltip as a string
    yLabel: String,

    // Index of the dataset the item comes from
    datasetIndex: Number,

    // Index of this data item in the dataset
    index: Number
}

Hover Configuration

The hover configuration is passed into the options.hover namespace. The global hover configuration is at Chart.defaults.global.hover.

Name Type Default Description
mode String 'single' Sets which elements hover. Acceptable options are 'single', 'label', or 'dataset'. single highlights the closest element. label highlights elements in all datasets at the same X value. dataset highlights the closest dataset.
animationDuration Number 400 Duration in milliseconds it takes to animate hover style changes
onHover Function null Called when any of the events fire. Called in the context of the chart and passed an array of active elements (bars, points, etc)

Animation Configuration

The following animation options are available. The global options for are defined in Chart.defaults.global.animation.

Name Type Default Description
duration Number 1000 The number of milliseconds an animation takes.
easing String "easeOutQuart" Easing function to use.
onProgress Function none Callback called on each step of an animation. Passed a single argument, an object, containing the chart instance and an object with details of the animation.
onComplete Function none Callback called at the end of an animation. Passed the same arguments as onProgress

Animation Callbacks

The onProgress and onComplete callbacks are useful for synchronizing an external draw to the chart animation. The callback is passed an object that implements the following interface. An example usage of these callbacks can be found on Github. This sample displays a progress bar showing how far along the animation is.

{
    // Chart object
    chartInstance,

    // Contains details of the on-going animation
    animationObject,
}

Animation Object

The animation object passed to the callbacks is of type Chart.Animation. The object has the following parameters.

{
    // Current Animation frame number
    currentStep: Number,

    // Number of animation frames
    numSteps: Number,

    // Animation easing to use
    easing: String,

    // Function that renders the chart
    render: Function,

    // User callback
    onAnimationProgress: Function,

    // User callback
    onAnimationComplete: Function
}

Element Configuration

The global options for elements are defined in Chart.defaults.global.elements.

Options can be configured for four different types of elements; arc, lines, points, and rectangles. When set, these options apply to all objects of that type unless specifically overridden by the configuration attached to a dataset.

Arc Configuration

Arcs are used in the polar area, doughnut and pie charts. They can be configured with the following options. The global arc options are stored in Chart.defaults.global.elements.arc.

Name Type Default Description
backgroundColor Color 'rgba(0,0,0,0.1)' Default fill color for arcs. Inherited from the global default
borderColor Color '#fff' Default stroke color for arcs
borderWidth Number 2 Default stroke width for arcs

Line Configuration

Line elements are used to represent the line in a line chart. The global line options are stored in Chart.defaults.global.elements.line.

Name Type Default Description
tension Number 0.4 Default bezier curve tension. Set to 0 for no bezier curves.
backgroundColor Color 'rgba(0,0,0,0.1)' Default line fill color
borderWidth Number 3 Default line stroke width
borderColor Color 'rgba(0,0,0,0.1)' Default line stroke color
borderCapStyle String 'butt' Default line cap style. See MDN
borderDash Array [] Default line dash. See MDN
borderDashOffset Number 0.0 Default line dash offset. See MDN
borderJoinStyle String 'miter' Default line join style. See MDN
fill Boolean true If true, the line is filled.

Point Configuration

Point elements are used to represent the points in a line chart or a bubble chart. The global point options are stored in Chart.defaults.global.elements.point.

Name Type Default Description
radius Number 3 Default point radius
pointStyle String 'circle' Default point style
backgroundColor Color 'rgba(0,0,0,0.1)' Default point fill color
borderWidth Number 1 Default point stroke width
borderColor Color 'rgba(0,0,0,0.1)' Default point stroke color
hitRadius Number 1 Extra radius added to point radius for hit detection
hoverRadius Number 4 Default point radius when hovered
hoverBorderWidth Number 1 Default stroke width when hovered

Rectangle Configuration

Rectangle elements are used to represent the bars in a bar chart. The global rectangle options are stored in Chart.defaults.global.elements.rectange.

Name Type Default Description
backgroundColor Color 'rgba(0,0,0,0.1)' Default bar fill color
borderWidth Number 0 Default bar stroke width
borderColor Color 'rgba(0,0,0,0.1)' Default bar stroke color
borderSkipped String 'bottom' Default skipped (excluded) border for rectangle. Can be one of bottom, left, top, right

Colors

When supplying colors to Chart options, you can use a number of formats. You can specify the color as a string in hexadecimal, RGB, or HSL notations. If a color is needed, but not specified, Chart.js will use the global default color. This color is stored at Chart.defaults.global.defaultColor. It is initially set to 'rgb(0, 0, 0, 0.1)';

You can also pass a CanvasGradient object. You will need to create this before passing to the chart, but using it you can achieve some interesting effects.

The final option is to pass a CanvasPattern object. For example, if you wanted to fill a dataset with a pattern from an image you could do the following.

var img = new Image();
img.src = 'https://example.com/my_image.png';
img.onload = function() {
    var ctx = document.getElementById('canvas').getContext('2d');
    var fillPattern = ctx.createPattern(img, 'repeat');

    var chart = new Chart(ctx, {
        data: {
            labels: ['Item 1', 'Item 2', 'Item 3'],
            datasets: [{
                data: [10, 20, 30],
                backgroundColor: fillPattern
            }]
        }
    })
}

Line Chart

Introduction

A line chart is a way of plotting data points on a line. Often, it is used to show trend data, and the comparison of two data sets.

Example Usage

var myLineChart = new Chart(ctx, {
    type: 'line',
    data: data,
    options: options
});

Alternatively a line chart can be created using syntax similar to the v1.0 syntax

var myLineChart = Chart.Line(ctx, {
    data: data,
    options: options
});

Data Structure

The following options can be included in a line chart dataset to configure options for that specific dataset.

All point* properties can be specified as an array. If these are set to an array value, the first value applies to the first point, the second value to the second point, and so on.

Property Type Usage
data See data point section The data to plot in a line
label String The label for the dataset which appears in the legend and tooltips
xAxisID String The ID of the x axis to plot this dataset on
yAxisID String The ID of the y axis to plot this dataset on
fill Boolean If true, fill the area under the line
lineTension Number Bezier curve tension of the line. Set to 0 to draw straightlines. Note This was renamed from 'tension' but the old name still works.
backgroundColor Color The fill color under the line. See Colors
borderWidth Number The width of the line in pixels
borderColor Color The color of the line.
borderCapStyle String Cap style of the line. See MDN
borderDash Array<Number> Length and spacing of dashes. See MDN
borderDashOffset Number Offset for line dashes. See MDN
borderJoinStyle String Line joint style. See MDN
pointBorderColor Color or Array<Color> The border color for points.
pointBackgroundColor Color or Array<Color> The fill color for points
pointBorderWidth Number or Array<Number> The width of the point border in pixels
pointRadius Number or Array<Number> The radius of the point shape. If set to 0, nothing is rendered.
pointHoverRadius Number or Array<Number> The radius of the point when hovered
pointHitRadius Number or Array<Number> The pixel size of the non-displayed point that reacts to mouse events
pointHoverBackgroundColor Color or Array<Color> Point background color when hovered
pointHoverBorderColor Color or Array<Color> Point border color when hovered
pointHoverBorderWidth Number or Array<Number> Border width of point when hovered
pointStyle String, Array<String>, Image, Array<Image> The style of point. Options are 'circle', 'triangle', 'rect', 'rectRot', 'cross', 'crossRot', 'star', 'line', and 'dash'. If the option is an image, that image is drawn on the canvas using drawImage.

An example data object using these attributes is shown below.

var data = {
    labels: ["January", "February", "March", "April", "May", "June", "July"],
    datasets: [
        {
            label: "My First dataset",
            fill: false,
            lineTension: 0.1,
            backgroundColor: "rgba(75,192,192,0.4)",
            borderColor: "rgba(75,192,192,1)",
            borderCapStyle: 'butt',
            borderDash: [],
            borderDashOffset: 0.0,
            borderJoinStyle: 'miter',
            pointBorderColor: "rgba(75,192,192,1)",
            pointBackgroundColor: "#fff",
            pointBorderWidth: 1,
            pointHoverRadius: 5,
            pointHoverBackgroundColor: "rgba(75,192,192,1)",
            pointHoverBorderColor: "rgba(220,220,220,1)",
            pointHoverBorderWidth: 2,
            pointRadius: 1,
            pointHitRadius: 10,
            data: [65, 59, 80, 81, 56, 55, 40],
        }
    ]
};

The line chart usually requires an array of labels. This labels are shown on the X axis. There must be one label for each data point. More labels than datapoints are allowed, in which case the line ends at the last data point. The data for line charts is broken up into an array of datasets. Each dataset has a colour for the fill, a colour for the line and colours for the points and strokes of the points. These colours are strings just like CSS. You can use RGBA, RGB, HEX or HSL notation.

The label key on each dataset is optional, and can be used when generating a scale for the chart.

Data Points

The data passed to the chart can be passed in two formats. The most common method is to pass the data array as an array of numbers. In this case, the data.labels array must be specified and must contain a label for each point.

The alternate is used for sparse datasets. Data is specified using an object containing x and y properties. This is used for scatter charts as documented below.

Scatter Line Charts

Scatter line charts can be created by changing the X axis to a linear axis. To use a scatter chart, data must be passed as objects containing X and Y properties. The example below creates a scatter chart with 3 points.

var scatterChart = new Chart(ctx, {
    type: 'line',
    data: {
        datasets: [{
            label: 'Scatter Dataset',
            data: [{
                x: -10,
                y: 0
            }, {
                x: 0,
                y: 10
            }, {
                x: 10,
                y: 5
            }]
        }]
    },
    options: {
        scales: {
            xAxes: [{
                type: 'linear',
                position: 'bottom'
            }]
        }
    }
});

Chart Options

These are the customisation options specific to Line charts. These options are merged with the global chart configuration options, and form the options of the chart.

Name Type Default Description
showLines Boolean true If false, the lines between points are not drawn

You can override these for your Chart instance by passing a member options into the Line method.

For example, we could have a line chart display without an X axis by doing the following. The config merge is smart enough to handle arrays so that you do not need to specify all axis settings to change one thing.

new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        scales: {
            xAxes: [{
                display: false
            }]
        }
    }
});

We can also change these defaults values for each Line type that is created, this object is available at Chart.defaults.line.

Stacked Charts

Stacked area charts can be created by setting the Y axis to a stacked configuration. The following example would have stacked lines.

var stackedLine = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        scales: {
            yAxes: [{
                stacked: true
            }]
        }
    }
});

Bar Chart

Introduction

A bar chart is a way of showing data as bars.

It is sometimes used to show trend data, and the comparison of multiple data sets side by side.

Example Usage

var myBarChart = new Chart(ctx, {
    type: 'bar',
    data: data,
    options: options
});

Or if you want horizontal bars.

var myBarChart = new Chart(ctx, {
    type: 'horizontalBar',
    data: data,
    options: options
});

Data Structure

The following options can be included in a bar chart dataset to configure options for that specific dataset.

Some properties can be specified as an array. If these are set to an array value, the first value applies to the first bar, the second value to the second bar, and so on.

Property Type Usage
data Array<Number> The data to plot as bars
label String The label for the dataset which appears in the legend and tooltips
xAxisID String The ID of the x axis to plot this dataset on
yAxisID String The ID of the y axis to plot this dataset on
backgroundColor Color or Array<Color> The fill color of the bars. See Colors
borderColor Color or Array<Color> Bar border color
borderWidth Number or Array<Number> Border width of bar in pixels
borderSkipped String or Array<String> Which edge to skip drawing the border for. Options are 'bottom', 'left', 'top', and 'right'
hoverBackgroundColor Color or Array<Color> Bar background color when hovered
hoverBorderColor Color or Array<Color> Bar border color when hovered
hoverBorderWidth Number or Array<Number> Border width of bar when hovered

An example data object using these attributes is shown below.

var data = {
    labels: ["January", "February", "March", "April", "May", "June", "July"],
    datasets: [
        {
            label: "My First dataset",
            backgroundColor: "rgba(255,99,132,0.2)",
            borderColor: "rgba(255,99,132,1)",
            borderWidth: 1,
            hoverBackgroundColor: "rgba(255,99,132,0.4)",
            hoverBorderColor: "rgba(255,99,132,1)",
            data: [65, 59, 80, 81, 56, 55, 40],
        }
    ]
};

The bar chart has the a very similar data structure to the line chart, and has an array of datasets, each with colours and an array of data. We have an array of labels too for display. In the example, we are showing the same data as the previous line chart example.

Chart Options

These are the customisation options specific to Bar charts. These options are merged with the global chart configuration options, and form the options of the chart.

The default options for bar chart are defined in Chart.defaults.bar.

Name Type Default Description
hover.mode String "label" Label's hover mode. "label" is used since the x axis displays data by the index in the dataset.
scales Object - -
scales.xAxes Array The bar chart officially supports only 1 x-axis but uses an array to keep the API consistent. Use a scatter chart if you need multiple x axes.
Options for xAxes
type String "Category" As defined in Scales.
display Boolean true If true, show the scale.
id String "x-axis-0" Id of the axis so that data can bind to it
stacked Boolean false If true, bars are stacked on the x-axis
categoryPercentage Number 0.8 Percent (0-1) of the available width (the space between the gridlines for small datasets) for each data-point to use for the bars. Read More
barPercentage Number 0.9 Percent (0-1) of the available width each bar should be within the category percentage. 1.0 will take the whole category width and put the bars right next to each other. Read More
gridLines Object See Scales
gridLines.offsetGridLines Boolean true If true, the bars for a particular data point fall between the grid lines. If false, the grid line will go right down the middle of the bars.
scales.yAxes Array [{ type: "linear" }]
Options for xAxes
type String "linear" As defined in Scales.
display Boolean true If true, show the scale.
id String "y-axis-0" Id of the axis so that data can bind to it.
stacked Boolean false If true, bars are stacked on the y-axis

You can override these for your Chart instance by passing a second argument into the Bar method as an object with the keys you want to override.

For example, we could have a bar chart without a stroke on each bar by doing the following:

new Chart(ctx, {
    type: "bar",
    data: data,
    options: {
        scales: {
                xAxes: [{
                        stacked: true
                }],
                yAxes: [{
                        stacked: true
                }]
            }
        }
    }
});
// This will create a chart with all of the default options, merged from the global config,
//  and the Bar chart defaults but this particular instance will have `stacked` set to true
// for both x and y axes.

We can also change these defaults values for each Bar type that is created, this object is available at Chart.defaults.bar. For horizontal bars, this object is available at Chart.defaults.horizontalBar.

The default options for horizontal bar charts are defined in Chart.defaults.horizontalBar and are same as those of the bar chart, but with xAxes and yAxes swapped and the following additional options.

Name Type Default Description
Options for xAxes
position String "bottom"
Options for yAxes
position String "left"

barPercentage vs categoryPercentage

The following shows the relationship between the bar percentage option and the category percentage option.

// categoryPercentage: 1.0
// barPercentage: 1.0
Bar:        | 1.0 | 1.0 |
Category:   |    1.0    |   
Sample:     |===========|

// categoryPercentage: 1.0
// barPercentage: 0.5
Bar:          |.5|  |.5|
Category:  |      1.0     |   
Sample:    |==============|

// categoryPercentage: 0.5
// barPercentage: 1.0
Bar:            |1.||1.|
Category:       |  .5  |   
Sample:     |==============|

Radar Chart

Introduction

A radar chart is a way of showing multiple data points and the variation between them.

They are often useful for comparing the points of two or more different data sets.

Example Usage

var myRadarChart = new Chart(ctx, {
    type: 'radar',
    data: data,
    options: options
});

Data Structure

The following options can be included in a radar chart dataset to configure options for that specific dataset.

All point* properties can be specified as an array. If these are set to an array value, the first value applies to the first point, the second value to the second point, and so on.

Property Type Usage
data Array<Number> The data to plot in a line
label String The label for the dataset which appears in the legend and tooltips
fill Boolean If true, fill the area under the line
lineTension Number Bezier curve tension of the line. Set to 0 to draw straightlines. Note This was renamed from 'tension' but the old name still works.
backgroundColor Color The fill color under the line. See Colors
borderWidth Number The width of the line in pixels
borderColor Color The color of the line.
borderCapStyle String Cap style of the line. See MDN
borderDash Array<Number> Length and spacing of dashes. See MDN
borderDashOffset Number Offset for line dashes. See MDN
borderJoinStyle String Line joint style. See MDN
pointBorderColor Color or Array<Color> The border color for points.
pointBackgroundColor Color or Array<Color> The fill color for points
pointBorderWidth Number or Array<Number> The width of the point border in pixels
pointRadius Number or Array<Number> The radius of the point shape. If set to 0, nothing is rendered.
pointHoverRadius Number or Array<Number> The radius of the point when hovered
hitRadius Number or Array<Number> The pixel size of the non-displayed point that reacts to mouse events
pointHoverBackgroundColor Color or Array<Color> Point background color when hovered
pointHoverBorderColor Color or Array<Color> Point border color when hovered
pointHoverBorderWidth Number or Array<Number> Border width of point when hovered
pointStyle String or Array<String> The style of point. Options include 'circle', 'triangle', 'rect', 'rectRot', 'cross', 'crossRot', 'star', 'line', and 'dash'

An example data object using these attributes is shown below.

var data = {
    labels: ["Eating", "Drinking", "Sleeping", "Designing", "Coding", "Cycling", "Running"],
    datasets: [
        {
            label: "My First dataset",
            backgroundColor: "rgba(179,181,198,0.2)",
            borderColor: "rgba(179,181,198,1)",
            pointBackgroundColor: "rgba(179,181,198,1)",
            pointBorderColor: "#fff",
            pointHoverBackgroundColor: "#fff",
            pointHoverBorderColor: "rgba(179,181,198,1)",
            data: [65, 59, 90, 81, 56, 55, 40]
        },
        {
            label: "My Second dataset",
            backgroundColor: "rgba(255,99,132,0.2)",
            borderColor: "rgba(255,99,132,1)",
            pointBackgroundColor: "rgba(255,99,132,1)",
            pointBorderColor: "#fff",
            pointHoverBackgroundColor: "#fff",
            pointHoverBorderColor: "rgba(255,99,132,1)",
            data: [28, 48, 40, 19, 96, 27, 100]
        }
    ]
};

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. 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. The label key on each dataset is optional, and can be used when generating a scale for the chart.

Chart Options

These are the customisation options specific to Radar charts. These options are merged with the global chart configuration options, and form the options of the chart.

The default options for radar chart are defined in Chart.defaults.radar.

Name Type Default Description
scale Object See Scales and Defaults for Radial Linear Scale Options for the one scale used on the chart. Use this to style the ticks, labels, and grid lines.
scale.type String "radialLinear" As defined in "Radial Linear".
elements.line Object Options for all line elements used on the chart, as defined in the global elements, duplicated here to show Radar chart specific defaults.
elements.line.lineTension Number 0 Tension exhibited by lines when calculating splineCurve. Setting to 0 creates straight lines.

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.

For example, we could have a radar chart without a point for each on piece of data by doing the following:

new Chart(ctx, {
    type: "radar",
    data: data,
    options: {
            scale: {
                reverse: true,
                ticks: {
                    beginAtZero: true
                }
            }
    }
});
// This will create a chart with all of the default options, merged from the global config,
//  and the Radar chart defaults but this particular instance's scale will be reversed as
// well as the ticks beginning at zero.

We can also change these defaults values for each Radar type that is created, this object is available at Chart.defaults.radar.

Polar Area Chart

Introduction

Polar area charts are similar to pie charts, but each segment has the same angle - the radius of the segment differs depending on the value.

This type of chart is often useful when we want to show a comparison data similar to a pie chart, but also show a scale of values for context.

Example Usage

new Chart(ctx, {
    data: data,
    type: 'polarArea',
    options: options
});

Data Structure

The following options can be included in a polar area chart dataset to configure options for that specific dataset.

Some properties are specified as arrays. The first value applies to the first bar, the second value to the second bar, and so on.

Property Type Usage
data Array<Number> The data to plot as bars
label String The label for the dataset which appears in the legend and tooltips
backgroundColor Array<Color> The fill color of the arcs. See Colors
borderColor Array<Color> Arc border color
borderWidth Array<Number> Border width of arcs in pixels
hoverBackgroundColor Array<Color> Arc background color when hovered
hoverBorderColor Array<Color> Arc border color when hovered
hoverBorderWidth Array<Number> Border width of arc when hovered

An example data object using these attributes is shown below.

var data = {
    datasets: [{
        data: [
            11,
            16,
            7,
            3,
            14
        ],
        backgroundColor: [
            "#FF6384",
            "#4BC0C0",
            "#FFCE56",
            "#E7E9ED",
            "#36A2EB"
        ],
        label: 'My dataset' // for legend
    }],
    labels: [
        "Red",
        "Green",
        "Yellow",
        "Grey",
        "Blue"
    ]
};

As you can see, for the chart data you pass in an array of objects, with a value and a colour. The value attribute should be a number, while the color attribute should be a string. Similar to CSS, for this string you can use HEX notation, RGB, RGBA or HSL.

Chart Options

These are the customisation options specific to Polar Area charts. These options are merged with the global chart configuration options, and form the options of the chart.

Name Type Default Description
scale Object See Scales and Defaults for Radial Linear Scale Options for the one scale used on the chart. Use this to style the ticks, labels, and grid.
scale.type String "radialLinear" As defined in "Radial Linear".
scale.lineArc Boolean true When true, lines are circular.
animation.animateRotate Boolean true If true, will animate the rotation of the chart.
animation.animateScale Boolean true If true, will animate scaling the chart.
legend.labels.generateLabels Function function(data) {} Returns labels for each the legend
legend.onClick Function function(event, legendItem) {} ` Handles clicking an individual legend item
legendCallback Function function(chart) Generates the HTML legend via calls to generateLegend

You can override these for your Chart instance by passing a second argument into the PolarArea method as an object with the keys you want to override.

For example, we could have a polar area chart with a black stroke on each segment like so:

new Chart(ctx, {
    data: data,
    type: "polarArea",
    options: {
        elements: {
            arc: {
                borderColor: "#000000"
            }
        }
    }
});
// This will create a chart with all of the default options, merged from the global config,
// and the PolarArea chart defaults but this particular instance will have `elements.arc.borderColor` set to `"#000000"`.

We can also change these defaults values for each PolarArea type that is created, this object is available at Chart.defaults.polarArea.

Pie & Doughnut Charts

Introduction

Pie and doughnut charts are probably the most commonly used chart there are. They are divided into segments, the arc of each segment shows the proportional value of each piece of data.

They are excellent at showing the relational proportions between data.

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.

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.


Example Usage

// For a pie chart
var myPieChart = new Chart(ctx,{
    type: 'pie',
    data: data,
    options: options
});
// And for a doughnut chart
var myDoughnutChart = new Chart(ctx, {
    type: 'doughnut',
    data: data,
    options: options
});

Data Structure

Property Type Usage
data Array<Number> The data to plot as bars
label String The label for the dataset which appears in the legend and tooltips
backgroundColor Array<Color> The fill color of the arcs. See Colors
borderColor Array<Color> Arc border color
borderWidth Array<Number> Border width of arcs in pixels
hoverBackgroundColor Array<Color> Arc background color when hovered
hoverBorderColor Array<Color> Arc border color when hovered
hoverBorderWidth Array<Number> Border width of arc when hovered

An example data object using these attributes is shown below.

var data = {
    labels: [
        "Red",
        "Blue",
        "Yellow"
    ],
    datasets: [
        {
            data: [300, 50, 100],
            backgroundColor: [
                "#FF6384",
                "#36A2EB",
                "#FFCE56"
            ],
            hoverBackgroundColor: [
                "#FF6384",
                "#36A2EB",
                "#FFCE56"
            ]
        }]
};

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. You can also add an array of background colors. The color attributes should be a string. Similar to CSS, for this string you can use HEX notation, RGB, RGBA or HSL.

Chart Options

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.

Name Type Default Description
cutoutPercentage Number 50 - for doughnut, 0 - for pie The percentage of the chart that is cut out of the middle.
rotation Number -0.5 * Math.PI Starting angle to draw arcs from
circumference Number 2 * Math.PI Sweep to allow arcs to cover
animation.animateRotate Boolean true If true, will animate the rotation of the chart.
animation.animateScale Boolean false If true, will animate scaling the Doughnut from the centre.
legend.labels.generateLabels Function function(chart) {} Returns a label for each item to be displayed on the legend.
legend.onClick Function function(event, legendItem) {} ` Handles clicking an individual legend item

You can override these for your Chart instance by passing a second argument into the Doughnut method as an object with the keys you want to override.

For example, we could have a doughnut chart that animates by scaling out from the centre like so:

new Chart(ctx,{
    type:"doughnut",
    animation:{
        animateScale:true
    }
});
// This will create a chart with all of the default options, merged from the global config,
// and the Doughnut chart defaults but this particular instance will have `animateScale` set to `true`.

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.

Scales

Scales in v2.0 of Chart.js are significantly more powerful, but also different than those of v1.0.

  • Multiple X & Y axes are supported.
  • A built-in label auto-skip feature detects would-be overlapping ticks and labels and removes every nth label to keep things displaying normally.
  • Scale titles are supported
  • New scale types can be extended without writing an entirely new chart type

Common Configuration

Every scale extends a core scale class with the following options:

Name Type Default Description
type String Chart specific. Type of scale being employed. Custom scales can be created and registered with a string key. Options: "category", "linear", "logarithmic", "time", "radialLinear"
display Boolean true If true, show the scale including gridlines, ticks, and labels. Overrides gridLines.display, scaleLabel.display, and ticks.display.
position String "left" Position of the scale. Possible values are 'top', 'left', 'bottom' and 'right'.
beforeUpdate Function undefined Callback called before the update process starts. Passed a single argument, the scale instance.
beforeSetDimensions Function undefined Callback that runs before dimensions are set. Passed a single argument, the scale instance.
afterSetDimensions Function undefined Callback that runs after dimensions are set. Passed a single argument, the scale instance.
beforeDataLimits Function undefined Callback that runs before data limits are determined. Passed a single argument, the scale instance.
afterDataLimits Function undefined Callback that runs after data limits are determined. Passed a single argument, the scale instance.
beforeBuildTicks Function undefined Callback that runs before ticks are created. Passed a single argument, the scale instance.
afterBuildTicks Function undefined Callback that runs after ticks are created. Useful for filtering ticks. Passed a single argument, the scale instance.
beforeTickToLabelConversion Function undefined Callback that runs before ticks are converted into strings. Passed a single argument, the scale instance.
afterTickToLabelConversion Function undefined Callback that runs after ticks are converted into strings. Passed a single argument, the scale instance.
beforeCalculateTickRotation Function undefined Callback that runs before tick rotation is determined. Passed a single argument, the scale instance.
afterCalculateTickRotation Function undefined Callback that runs after tick rotation is determined. Passed a single argument, the scale instance.
beforeFit Function undefined Callback that runs before the scale fits to the canvas. Passed a single argument, the scale instance.
afterFit Function undefined Callback that runs after the scale fits to the canvas. Passed a single argument, the scale instance.
afterUpdate Function undefined Callback that runs at the end of the update process. Passed a single argument, the scale instance.
gridLines Object - See grid line configuration section.
scaleLabel Object See scale title configuration section.
ticks Object See ticks configuration section.

Grid Line Configuration

The grid line configuration is nested under the scale configuration in the gridLines key. It defines options for the grid lines that run perpendicular to the axis.

Name Type Default Description
display Boolean true
color Color "rgba(0, 0, 0, 0.1)" Color of the grid lines.
lineWidth Number 1 Stroke width of grid lines
drawBorder Boolean true If true draw border on the edge of the chart
drawOnChartArea Boolean true If true, draw lines on the chart area inside the axis lines. This is useful when there are multiple axes and you need to control which grid lines are drawn
drawTicks Boolean true If true, draw lines beside the ticks in the axis area beside the chart.
tickMarkLength Number 10 Length in pixels that the grid lines will draw into the axis area.
zeroLineWidth Number 1 Stroke width of the grid line for the first index (index 0).
zeroLineColor Color "rgba(0, 0, 0, 0.25)" Stroke color of the grid line for the first index (index 0).
offsetGridLines Boolean false If true, offset labels from grid lines.

Scale Title Configuration

The grid line configuration is nested under the scale configuration in the scaleLabel key. It defines options for the scale title.

Name Type Default Description
display Boolean false
labelString String "" The text for the title. (i.e. "# of People", "Response Choices")
fontColor Color "#666" Font color for the scale title.
fontFamily String "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif" Font family for the scale title, follows CSS font-family options.
fontSize Number 12 Font size for the scale title.
fontStyle String "normal" Font style for the scale title, follows CSS font-style options (i.e. normal, italic, oblique, initial, inherit).

Tick Configuration

The grid line configuration is nested under the scale configuration in the ticks key. It defines options for the tick marks that are generated by the axis.

Name Type Default Description
autoSkip Boolean true If true, automatically calculates how many labels that can be shown and hides labels accordingly. Turn it off to show all labels no matter what
callback Function function(value) { return '' + value; } Returns the string representation of the tick value as it should be displayed on the chart. See callback section below.
display Boolean true If true, show the ticks.
fontColor Color "#666" Font color for the tick labels.
fontFamily String "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif" Font family for the tick labels, follows CSS font-family options.
fontSize Number 12 Font size for the tick labels.
fontStyle String "normal" Font style for the tick labels, follows CSS font-style options (i.e. normal, italic, oblique, initial, inherit).
labelOffset Number 0 Distance in pixels to offset the label from the centre point of the tick (in the y direction for the x axis, and the x direction for the y axis). Note: this can cause labels at the edges to be cropped by the edge of the canvas
maxRotation Number 90 Maximum rotation for tick labels when rotating to condense labels. Note: Rotation doesn't occur until necessary. Note: Only applicable to horizontal scales.
minRotation Number 0 Minimum rotation for tick labels. Note: Only applicable to horizontal scales.
mirror Boolean false Flips tick labels around axis, displaying the labels inside the chart instead of outside. Note: Only applicable to vertical scales.
padding Number 10 Padding between the tick label and the axis. Note: Only applicable to horizontal scales.
reverse Boolean false Reverses order of tick labels.

Creating Custom Tick Formats

The callback method may be used for advanced tick customization. In the following example, every label of the Y axis would be displayed in scientific notation.

If the callback returns null or undefined the associated grid line will be hidden.

var chartInstance = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        scales: {
            yAxes: [{
                ticks: {
                    // Create scientific notation labels
                    callback: function(value, index, values) {
                        return value.toExponential();
                    }
                }
            }]
        }
    }
});

Category Scale

The category scale will be familiar to those who have used v1.0. Labels are drawn in from the labels array included in the chart data.

Configuration Options

The category scale has the following additional options that can be set.

Name Type Default Description
ticks.min String - The minimum item to display. Must be a value in the labels array
ticks.max String - The maximum item to display. Must be a value in the labels array
gridLines.offsetGridLines Boolean - If true, labels are shifted to be between grid lines. This is used in the bar chart.

Linear Scale

The linear scale is use to chart numerical data. It can be placed on either the x or y axis. The scatter chart type automatically configures a line chart to use one of these scales for the x axis. As the name suggests, linear interpolation is used to determine where a value lies on the axis.

Configuration Options

The following options are provided by the linear scale. They are all located in the ticks sub options.

Name Type Default Description
beginAtZero Boolean - if true, scale will inclulde 0 if it is not already included.
min Number - User defined minimum number for the scale, overrides minimum value from data.
max Number - User defined maximum number for the scale, overrides maximum value from data.
maxTicksLimit Number 11 Maximum number of ticks and gridlines to show. If not defined, it will limit to 11 ticks but will show all gridlines.
stepSize Number - User defined fixed step size for the scale. If set, the scale ticks will be enumerated by multiple of stepSize, having one tick per increment. If not set, the ticks are labeled automatically using the nice numbers algorithm.
stepSize Number - if defined, it can be used along with the min and the max to give a custom number of steps. See the example below.
suggestedMax Number - User defined maximum number for the scale, overrides maximum value except for if it is lower than the maximum value.
suggestedMin Number - User defined minimum number for the scale, overrides minimum value except for if it is higher than the minimum value.

Example Configuration

The following example creates a line chart with a vertical axis that goes from 0 to 5 in 0.5 sized steps.

var chartInstance = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        scales: {
            yAxes: [{
                ticks: {
                    max: 5,
                    min: 0,
                    stepSize: 0.5
                }
            }]
        }
    }
});

Logarithmic Scale

The logarithmic scale is use to chart numerical data. It can be placed on either the x or y axis. As the name suggests, logarithmic interpolation is used to determine where a value lies on the axis.

Configuration Options

The following options are provided by the logarithmic scale. They are all located in the ticks sub options.

Name Type Default Description
min Number - User defined minimum number for the scale, overrides minimum value from data.
max Number - User defined maximum number for the scale, overrides maximum value from data.

Example Configuration

The following example creates a chart with a logarithmic X axis that ranges from 1 to 1000.

var chartInstance = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        xAxes: [{
            type: 'logarithmic',
            position: 'bottom',
            ticks: {
                min: 1,
                max: 1000
            }
        }]
    }
})

Time Scale

The time scale is used to display times and dates. It can only be placed on the X axis. When building its ticks, it will automatically calculate the most comfortable unit base on the size of the scale.

Configuration Options

The following options are provided by the logarithmic scale. They are all located in the time sub options.

Name Type Default Description
displayFormats Object - See Display Formats section below.
isoWeekday Boolean false If true and the unit is set to 'week', iso weekdays will be used.
max Time - If defined, this will override the data maximum
min Time - If defined, this will override the data minimum
parser String or Function - If defined as a string, it is interpreted as a custom format to be used by moment to parse the date. If this is a function, it must return a moment.js object given the appropriate data value.
round String - If defined, dates will be rounded to the start of this unit. See Time Units below for the allowed units.
tooltipFormat String '' The moment js format string to use for the tooltip.
unit String - If defined, will force the unit to be a certain type. See Time Units section below for details.
unitStepSize Number 1 The number of units between grid lines.

Date Formats

When providing data for the time scale, Chart.js supports all of the formats that Moment.js accepts. See Moment.js docs for details.

Display Formats

The following display formats are used to configure how different time units are formed into strings for the axis tick marks. See moment.js for the allowable format strings.

Name Default
millisecond 'SSS [ms]'
second 'h:mm:ss a'
minute 'h:mm:ss a'
hour 'MMM D, hA'
day 'll'
week 'll'
month 'MMM YYYY'
quarter '[Q]Q - YYYY'
year 'YYYY'

For example, to set the display format for the 'quarter' unit to show the month and year, the following config would be passed to the chart constructor.

var chartInstance = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        scales: {
            xAxes: [{
                type: 'time',
                time: {
                    displayFormats: {
                        quarter: 'MMM YYYY'
                    }
                }
            }]
        }
    }
})

Time Units

The following time measurements are supported. The names can be passed as strings to the time.unit config option to force a certain unit.

  • millisecond
  • second
  • minute
  • hour
  • day
  • week
  • month
  • quarter
  • year

For example, to create a chart with a time scale that always displayed units per month, the following config could be used.

var chartInstance = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        scales: {
            xAxes: [{
                time: {
                    unit: 'month'
                }
            }]
        }
    }
})

Radial Linear Scale

The radial linear scale is used specifically for the radar and polar are chart types. It overlays the chart area, rather than being positioned on one of the edges.

Configuration Options

The following additional configuration options are provided by the radial linear scale.

Name Type Default Description
lineArc Boolean false If true, circular arcs are used else straight lines are used. The former is used by the polar area chart and the latter by the radar chart
angleLines Object - See the Angle Lines section below for details.
pointLabels Object - See the Point Label section below for details.
ticks Object - See the Ticks table below for options.

Angle Line Options

The following options are used to configure angled lines that radiate from the center of the chart to the point labels. They can be found in the angleLines sub options. Note that these options only apply if lineArc is false.

Name Type Default Description
display Boolean true If true, angle lines are shown.
color Color 'rgba(0, 0, 0, 0.1)' Color of angled lines
lineWidth Number 1 Width of angled lines

Point Label Options

The following options are used to configure the point labels that are shown on the perimeter of the scale. They can be found in the pointLabel sub options. Note that these options only apply if lineArc is false.

Name Type Default Description
callback Function - Callback function to transform data label to axis label
fontColor Color '#666' Font color
fontFamily String "'Helvetica Neue', 'Helvetica', 'Arial', sans-serif" Font family to render
fontSize Number 10 Font size in pixels
fontStyle String 'normal' Font Style to use

Tick Options

Name Type Default Description
backdropColor Color 'rgba(255, 255, 255, 0.75)' Color of label backdrops
backdropPaddingX Number 2 Horizontal padding of label backdrop
backdropPaddingY Number 2 Vertical padding of label backdrop
maxTicksLimit Number 11 Maximum number of ticks and gridlines to show. If not defined, it will limit to 11 ticks but will show all gridlines.
showLabelBackdrop Boolean true If true, draw a background behind the tick labels

Update Default Scale config

The default configuration for a scale can be easily changed using the scale service. Pass in a partial configuration that will be merged with the current scale default configuration.

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.

Chart.scaleService.updateScaleDefaults('linear', {
    ticks: {
        min: 0
    }
})

Advanced usage

Prototype Methods

For each chart, there are a set of global prototype methods on the shared ChartType which you may find useful. These are available on all charts created with Chart.js, but for the examples, let's use a line chart we've made.

// For example:
var myLineChart = new Chart(ctx, config);

.destroy()

Use this to destroy any chart instances that are created. This will clean up any references stored to the chart object within Chart.js, along with any associated event listeners attached by Chart.js. This must be called before the canvas is reused for a new chart.

// Destroys a specific chart instance
myLineChart.destroy();

.update(duration, lazy)

Triggers an update of the chart. This can be safely called after replacing the entire data object. This will update all scales, legends, and then re-render the chart.

// duration is the time for the animation of the redraw in miliseconds
// lazy is a boolean. if true, the animation can be interupted by other animations
myLineChart.data.datasets[0].data[2] = 50; // Would update the first dataset's value of 'March' to be 50
myLineChart.update(); // Calling update now animates the position of March from 90 to 50.

.render(duration, lazy)

Triggers a redraw of all chart elements. Note, this does not update elements for new data. Use .update() in that case.

// duration is the time for the animation of the redraw in miliseconds
// lazy is a boolean. if true, the animation can be interupted by other animations
myLineChart.render(duration, lazy);

.stop()

Use this to stop any current animation loop. This will pause the chart during any current animation frame. Call .render() to re-animate.

// Stops the charts animation loop at its current frame
myLineChart.stop();
// => returns 'this' for chainability

.resize()

Use this to manually resize the canvas element. This is run each time the canvas container is resized, but you can call this method manually if you change the size of the canvas nodes container element.

// Resizes & redraws to fill its container element
myLineChart.resize();
// => returns 'this' for chainability

.clear()

Will clear the chart canvas. Used extensively internally between animation frames, but you might find it useful.

// Will clear the canvas that myLineChart is drawn on
myLineChart.clear();
// => returns 'this' for chainability

.toBase64Image()

This returns a base 64 encoded string of the chart in it's current state.

myLineChart.toBase64Image();
// => returns png data url of the image on the canvas

.generateLegend()

Returns an HTML string of a legend for that chart. The legend is generated from the legendCallback in the options.

myLineChart.generateLegend();
// => returns HTML string of a legend for this chart

.getElementAtEvent(e)

Calling getElementAtEvent(event) on your Chart instance passing an argument of an event, or jQuery event, will return the single element at the event position. If there are multiple items within range, only the first is returned

myLineChart.getElementAtEvent(e);
// => returns the first element at the event point.

.getElementsAtEvent(e)

Looks for the element under the event point, then returns all elements at the same data index. This is used internally for 'label' mode highlighting.

Calling getElementsAtEvent(event) on your Chart instance passing an argument of an event, or jQuery event, will return the point elements that are at that the same position of that event.

canvas.onclick = function(evt){
    var activePoints = myLineChart.getElementsAtEvent(evt);
    // => activePoints is an array of points on the canvas that are at the same position as the click event.
};

This functionality may be useful for implementing DOM based tooltips, or triggering custom behaviour in your application.

.getDatasetAtEvent(e)

Looks for the element under the event point, then returns all elements from that dataset. This is used internally for 'dataset' mode highlighting

myLineChart.getDatasetAtEvent(e);
// => returns an array of elements

External Tooltips

You can enable custom tooltips in the global or chart configuration like so:

var myPieChart = new Chart(ctx, {
    type: 'pie',
    data: data,
    options: {
        tooltips: {
            custom: function(tooltip) {
                // tooltip will be false if tooltip is not visible or should be hidden
                if (!tooltip) {
                    return;
                }

                // Otherwise, tooltip will be an object with all tooltip properties like:

                // tooltip.caretSize
                // tooltip.caretPadding
                // tooltip.chart
                // tooltip.cornerRadius
                // tooltip.fillColor
                // tooltip.font...
                // tooltip.text
                // tooltip.x
                // tooltip.y
                // etc...
            }
        }
    }
});

See sample/line-customTooltips.html for examples on how to get started.

Writing New Scale Types

Starting with Chart.js 2.0 scales can be individually extended. Scales should always derive from Chart.Scale.

var MyScale = Chart.Scale.extend({
    /* extensions ... */
});

// MyScale is now derived from Chart.Scale

Once you have created your scale class, you need to register it with the global chart object so that it can be used. A default config for the scale may be provided when registering the constructor. The first parameter to the register function is a string key that is used later to identify which scale type to use for a chart.

Chart.scaleService.registerScaleType('myScale', MyScale, defaultConfigObject);

To use the new scale, simply pass in the string key to the config when creating a chart.

var lineChart = new Chart(ctx, {
    data: data,
    type: 'line',
    options: {
        scales: {
            yAxes: [{
                type: 'myScale' // this is the same key that was passed to the registerScaleType function
            }]
        }
    }
})

Scale Properties

Scale instances are given the following properties during the fitting process.

{
    left: Number, // left edge of the scale bounding box
    right: Number, // right edge of the bounding box'
    top: Number, 
    bottom: Number,
    width: Number, // the same as right - left
    height: Number, // the same as bottom - top

    // Margin on each side. Like css, this is outside the bounding box. 
    margins: {
        left: Number,
        right: Number,
        top: Number,
        bottom: Number,
    },

    // Amount of padding on the inside of the bounding box (like CSS)
    paddingLeft: Number,
    paddingRight: Number,
    paddingTop: Number,
    paddingBottom: Number,
}

Scale Interface

To work with Chart.js, custom scale types must implement the following interface.

{
    // Determines the data limits. Should set this.min and this.max to be the data max/min
    determineDataLimits: function() {},

    // Generate tick marks. this.chart is the chart instance. The data object can be accessed as this.chart.data
    // buildTicks() should create a ticks array on the axis instance, if you intend to use any of the implementations from the base class
    buildTicks: function() {},

    // Get the value to show for the data at the given index of the the given dataset, ie this.chart.data.datasets[datasetIndex].data[index]
    getLabelForIndex: function(index, datasetIndex) {},

    // Get the pixel (x coordinate for horizontal axis, y coordinate for vertical axis) for a given value
    // @param index: index into the ticks array
    // @param includeOffset: if true, get the pixel halway between the given tick and the next
    getPixelForTick: function(index, includeOffset) {},

    // Get the pixel (x coordinate for horizontal axis, y coordinate for vertical axis) for a given value
    // @param value : the value to get the pixel for
    // @param index : index into the data array of the value
    // @param datasetIndex : index of the dataset the value comes from
    // @param includeOffset : if true, get the pixel halway between the given tick and the next
    getPixelForValue: function(value, index, datasetIndex, includeOffset) {}

    // Get the value for a given pixel (x coordinate for horizontal axis, y coordinate for vertical axis)
    // @param pixel : pixel value
    getValueForPixel: function(pixel) {}
}

Optionally, the following methods may also be overwritten, but an implementation is already provided by the Chart.Scale base class.

    // Transform the ticks array of the scale instance into strings. The default implementation simply calls this.options.ticks.callback(numericalTick, index, ticks); 
    convertTicksToLabels: function() {},

    // Determine how much the labels will rotate by. The default implementation will only rotate labels if the scale is horizontal. 
    calculateTickRotation: function() {},

    // Fits the scale into the canvas.
    // this.maxWidth and this.maxHeight will tell you the maximum dimensions the scale instance can be. Scales should endeavour to be as efficient as possible with canvas space.
    // this.margins is the amount of space you have on either side of your scale that you may expand in to. This is used already for calculating the best label rotation
    // You must set this.minSize to be the size of your scale. It must be an object containing 2 properties: width and height.
    // You must set this.width to be the width and this.height to be the height of the scale
    fit: function() {},

    // Draws the scale onto the canvas. this.(left|right|top|bottom) will have been populated to tell you the area on the canvas to draw in
    // @param chartArea : an object containing four properties: left, right, top, bottom. This is the rectangle that lines, bars, etc will be drawn in. It may be used, for example, to draw grid lines.
    draw: function(chartArea) {},

The Core.Scale base class also has some utility functions that you may find useful.

{    
    // Returns true if the scale instance is horizontal
    isHorizontal: function() {},

    // Get the correct value from the value from this.chart.data.datasets[x].data[]
    // If dataValue is an object, returns .x or .y depending on the return of isHorizontal()
    // If the value is undefined, returns NaN
    // Otherwise returns the value.
    // Note that in all cases, the returned value is not guaranteed to be a Number
    getRightValue: function(dataValue) {},
}

Writing New Chart Types

Chart.js 2.0 introduces the concept of controllers for each dataset. Like scales, new controllers can be written as needed.

Chart.controllers.MyType = Chart.DatasetController.extend({

});


// Now we can create a new instance of our chart, using the Chart.js API
new Chart(ctx, {
    // this is the string the constructor was registered at, ie Chart.controllers.MyType
    type: 'MyType',
    data: data,
    options: options
});

Dataset Controller Interface

Dataset controllers must implement the following interface.

{
    // Create elements for each piece of data in the dataset. Store elements in an array on the dataset as dataset.metaData
    addElements: function() {},

    // Create a single element for the data at the given index and reset its state
    addElementAndReset: function(index) {},

    // Draw the representation of the dataset
    // @param ease : if specified, this number represents how far to transition elements. See the implementation of draw() in any of the provided controllers to see how this should be used
    draw: function(ease) {},

    // Remove hover styling from the given element
    removeHoverStyle: function(element) {},

    // Add hover styling to the given element
    setHoverStyle: function(element) {},

    // Update the elements in response to new data
    // @param reset : if true, put the elements into a reset state so they can animate to their final values
    update: function(reset) {},
}

The following methods may optionally be overridden by derived dataset controllers

{
    // Initializes the controller
    initialize: function(chart, datasetIndex) {},

    // Ensures that the dataset represented by this controller is linked to a scale. Overridden to helpers.noop in the polar area and doughnut controllers as these
    // chart types using a single scale
    linkScales: function() {},

    // Called by the main chart controller when an update is triggered. The default implementation handles the number of data points changing and creating elements appropriately. 
    buildOrUpdateElements: function() {}
}

Extending Existing Chart Types

Extending or replacing an existing controller type is easy. Simply replace the constructor for one of the built in types with your own.

The built in controller types are:

  • Chart.controllers.line
  • Chart.controllers.bar
  • Chart.controllers.radar
  • Chart.controllers.doughnut
  • Chart.controllers.polarArea
  • Chart.controllers.bubble

Bar Controller

The bar controller has a special property that you should be aware of. To correctly calculate the width of a bar, the controller must determine the number of datasets that map to bars. To do this, the bar controller attaches a property bar to the dataset during initialization. If you are creating a replacement or updated bar controller, you should do the same. This will ensure that charts with regular bars and your new derived bars will work seamlessly.

Creating Plugins

Starting with v2.1.0, you can create plugins for chart.js. To register your plugin, simply call Chart.pluginService.register and pass your plugin in. Plugins will be called at the following times

  • Start of initialization
  • End of initialization
  • Start of update
  • After the chart scales have calculated
  • End of update (before render occurs)
  • Start of draw
  • End of draw
  • Before an animation is started

Plugins should derive from Chart.PluginBase and implement the following interface

{
    beforeInit: function(chartInstance) { },
    afterInit: function(chartInstance) { },

    beforeUpdate: function(chartInstance) { },
    afterScaleUpdate: function(chartInstance) { }
    afterUpdate: function(chartInstance) { },

    // This is called at the start of a render. It is only called once, even if the animation will run for a number of frames. Use beforeDraw or afterDraw 
    // to do something on each animation frame
    beforeRender: function(chartInstance) { },

    // Easing is for animation
    beforeDraw: function(chartInstance, easing) { },
    afterDraw: function(chartInstance, easing) { }

    destroy: function(chartInstance) { }
}

Building Chart.js

Chart.js uses gulp to build the library into a single JavaScript file.

Firstly, we need to ensure development dependencies are installed. With node and npm installed, after cloning the Chart.js repo to a local directory, and navigating to that directory in the command line, we can run the following:

npm install
npm install -g gulp

This will install the local development dependencies for Chart.js, along with a CLI for the JavaScript task runner gulp.

Now, we can run the gulp build task.

gulp build

Notes

Previous versions

Please note - documentation for previous versions are available on the GitHub repo. Version 1.x may continue to receive updates for bug fixes or high priority items.

Browser support

Chart.js offers support for all browsers where canvas is supported.

Browser support for the canvas element is available in all modern & major mobile browsers (http://caniuse.com/#feat=canvas).

Thanks to BrowserStack for allowing our team to test on thousands of browsers.

Bugs & issues

Please report these on the GitHub page - at github.com/chartjs/Chart.js. If you could include a link to a simple jsbin or similar to demonstrate the issue, that'd be really helpful.

Contributing

New contributions to the library are welcome, just a couple of guidelines:

  • Tabs for indentation, not spaces please.
  • Please ensure you're changing the individual files in /src, not the concatenated output in the Chart.js file in the root of the repo.
  • Please check that your code will pass jshint code standards, gulp jshint will run this for you.
  • Please keep pull requests concise, and document new functionality in the relevant .md file.
  • Consider whether your changes are useful for all users, or if creating a Chart.js extension would be more appropriate.

License

Chart.js is open source and available under the MIT license.