Chart.js/docs/03-Bar-Chart.md

title	anchor
Bar Chart	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
});

Data structure

var data = {
	labels: ["January", "February", "March", "April", "May", "June", "July"],
	datasets: [
		{
			label: "My First dataset",

			// The properties below allow an array to be specified to change the value of the item at the given index
			// String  or array - the bar color
			backgroundColor: "rgba(220,220,220,0.2)",

			// String or array - bar stroke color
			borderColor: "rgba(220,220,220,1)",

			// Number or array - bar border width
			borderWidth: 1,

			// String or array - fill color when hovered
			hoverBackgroundColor: "rgba(220,220,220,0.2)",

			// String or array - border color when hovered
			hoverBorderColor: "rgba(220,220,220,1)",

			// The actual data
			data: [65, 59, 80, 81, 56, 55, 40],

			// String - If specified, binds the dataset to a certain y-axis. If not specified, the first y-axis is used.
			yAxisID: "y-axis-1",
		},
		{
			label: "My Second dataset",
			backgroundColor: "rgba(220,220,220,0.2)",
			borderColor: "rgba(220,220,220,1)",
			borderWidth: 1,
			hoverBackgroundColor: "rgba(220,220,220,0.2)",
			hoverBorderColor: "rgba(220,220,220,1)",
			data: [28, 48, 40, 19, 86, 27, 90]
		}
	]
};

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. Again, colours are in CSS format. We have an array of labels too for display. In the example, we are showing the same data as the previous line chart example.

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 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
stacked	Boolean	false
hover.mode	String	"label"	Label's hover mode. "label" is used since the x axis displays data by the index in the dataset.
scales	Array	-	-
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.
position	String	"bottom"	Position of the scale. Options are "top" and "bottom" for dataset scales.
id	String	"x-axis-1"	Id of the axis so that data can bind to it
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	Array	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.
scaleLabel	Array	See Scales
ticks	Array	See Scales
scales.yAxes	Array	[{ type: "linear" }]
Options for xAxes
type	String	"linear"	As defined in Scales.
display	Boolean	true	If true, show the scale.
position	String	"left"	Position of the scale. Options are "left" and "right" for dataset scales.
id	String	"y-axis-1"	Id of the axis so that data can bind to it.
gridLines	Array	See Scales
scaleLabel	Array	See Scales
ticks	Array	See Scales

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.

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:	   |==============|