150 lines
4.9 KiB
Markdown
Executable File
150 lines
4.9 KiB
Markdown
Executable File
---
|
|
title: Bar Chart
|
|
anchor: 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.
|
|
|
|
<div class="canvas-holder">
|
|
<canvas width="250" height="125"></canvas>
|
|
</div>
|
|
|
|
### Example usage
|
|
```javascript
|
|
var myBarChart = new Chart(ctx).Bar(data, options);
|
|
```
|
|
|
|
### Data structure
|
|
|
|
```javascript
|
|
var data = {
|
|
labels: ["January", "February", "March", "April", "May", "June", "July"],
|
|
datasets: [
|
|
{
|
|
label: "My First dataset",
|
|
fillColor: "rgba(220,220,220,0.5)",
|
|
strokeColor: "rgba(220,220,220,0.8)",
|
|
highlightFill: "rgba(220,220,220,0.75)",
|
|
highlightStroke: "rgba(220,220,220,1)",
|
|
data: [65, 59, 80, 81, 56, 55, 40]
|
|
},
|
|
{
|
|
label: "My Second dataset",
|
|
fillColor: "rgba(151,187,205,0.5)",
|
|
strokeColor: "rgba(151,187,205,0.8)",
|
|
highlightFill: "rgba(151,187,205,0.75)",
|
|
highlightStroke: "rgba(151,187,205,1)",
|
|
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](#getting-started-global-chart-configuration), and form the options of the chart.
|
|
|
|
```javascript
|
|
{
|
|
//Boolean - Whether the scale should start at zero, or an order of magnitude down from the lowest value
|
|
scaleBeginAtZero : true,
|
|
|
|
//Boolean - Whether grid lines are shown across the chart
|
|
scaleShowGridLines : true,
|
|
|
|
//String - Colour of the grid lines
|
|
scaleGridLineColor : "rgba(0,0,0,.05)",
|
|
|
|
//Number - Width of the grid lines
|
|
scaleGridLineWidth : 1,
|
|
|
|
//Boolean - Whether to show horizontal lines (except X axis)
|
|
scaleShowHorizontalLines: true,
|
|
|
|
//Boolean - Whether to show vertical lines (except Y axis)
|
|
scaleShowVerticalLines: true,
|
|
|
|
//Boolean - If there is a stroke on each bar
|
|
barShowStroke : true,
|
|
|
|
//Number - Pixel width of the bar stroke
|
|
barStrokeWidth : 2,
|
|
|
|
//Number - Spacing between each of the X value sets
|
|
barValueSpacing : 5,
|
|
|
|
//Number - Spacing between data sets within X values
|
|
barDatasetSpacing : 1,
|
|
{% raw %}
|
|
//String - A legend template
|
|
legendTemplate : "<ul class=\"<%=name.toLowerCase()%>-legend\"><% for (var i=0; i<datasets.length; i++){%><li><span style=\"background-color:<%=datasets[i].fillColor%>\"></span><%if(datasets[i].label){%><%=datasets[i].label%><%}%></li><%}%></ul>"
|
|
{% endraw %}
|
|
}
|
|
```
|
|
|
|
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:
|
|
|
|
```javascript
|
|
new Chart(ctx).Bar(data, {
|
|
barShowStroke: false
|
|
});
|
|
// 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 `barShowStroke` set to false.
|
|
```
|
|
|
|
We can also change these defaults values for each Bar type that is created, this object is available at `Chart.defaults.Bar`.
|
|
|
|
### Prototype methods
|
|
|
|
#### .getBarsAtEvent( event )
|
|
|
|
Calling `getBarsAtEvent(event)` on your Chart instance passing an argument of an event, or jQuery event, will return the bar elements that are at that the same position of that event.
|
|
|
|
```javascript
|
|
canvas.onclick = function(evt){
|
|
var activeBars = myBarChart.getBarsAtEvent(evt);
|
|
// => activeBars is an array of bars 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.
|
|
|
|
#### .update( )
|
|
|
|
Calling `update()` on your Chart instance will re-render the chart with any updated values, allowing you to edit the value of multiple existing points, then render those in one animated render loop.
|
|
|
|
```javascript
|
|
myBarChart.datasets[0].bars[2].value = 50;
|
|
// Would update the first dataset's value of 'March' to be 50
|
|
myBarChart.update();
|
|
// Calling update now animates the position of March from 90 to 50.
|
|
```
|
|
|
|
#### .addData( valuesArray, label )
|
|
|
|
Calling `addData(valuesArray, label)` on your Chart instance passing an array of values for each dataset, along with a label for those bars.
|
|
|
|
```javascript
|
|
// The values array passed into addData should be one for each dataset in the chart
|
|
myBarChart.addData([40, 60], "August");
|
|
// The new data will now animate at the end of the chart.
|
|
```
|
|
|
|
#### .removeData( )
|
|
|
|
Calling `removeData()` on your Chart instance will remove the first value for all datasets on the chart.
|
|
|
|
```javascript
|
|
myBarChart.removeData();
|
|
// The chart will now animate and remove the first bar
|
|
```
|