Pie chart API reference

Summary: Documentation about the Pie chart including information about all of the options that are available to you. The Pie chart can show a single dataset and with the donut option it can show multiple datasets. Some people find them to be quite contentious though as comparing individual pieces of data can be tricky.

• Example
• Properties
• Methods
• The Horseshoe Meter
• Animation effects

Example

<script>
    data = [564,155,499,611,322];

    new RGraph.Pie({
        id: 'cvs',
        data: data,
        options: {
            labels: ['Abc', 'Def', 'Ghi', 'Jkl', 'Mno'],
            linewidth: 2,
            colorsStroke: 'white'
        }
    }).draw();
</script>

Properties

You can use these properties to control how the pie chart looks. You can set them by using the set() method. Eg:

obj.set('name', 'value');

• Chart configuration properties
• Margin properties
• Color properties
• Labels and text properties
• Title properties
• Shadow properties
• Interactive features properties
• Key properties
• Event properties
• Miscellaneous properties

Chart configuration properties

Margin properties

Color properties

Labels and text properties

<div style="margin-left: 50px; display: inline-block">
    <canvas id="cvs" width="650" height="250"></canvas>
</div>

<div style="margin-left: 50px; display: inline-block">
    <canvas id="cvs" width="650" height="250"></canvas>
</div>

Title properties

Shadow properties

Interactive features properties

Key properties

Event properties

Miscellaneous properties

Methods

obj.set(name, value)
An accessor that you can use to set the values of properties.

obj.getShape(event)

obj.getSegment() makes it easy to determine which segment of the Pie chart was clicked on. It provides:

• Originating X coordinate
• Originating Y coordinate
• The radius of the segment
• The starting angle (measured in radians)
• The ending angle (measured in radians)
• The zero-indexed segment number

The shape also includes textual indexes like this: shape['object'] And they are:

• object
• x
• y
• radius
• angle.start
• angle.end
• tooltip
• index

<script>
    RGraph.register(myGraph);
    
    myGraph.canvas.onclick = function (e)
    {
        RGraph.fixEventObject(e);
        RGraph.redraw();

        var ca  = e.target;
        var co  = ca.getContext('2d');
        var obj = ca.__object__;
        var segment = obj.getShape(e);
        
        if (segment) {
            co.fillStyle = 'rgba(255,255,255,0.5)';
            co.beginPath();            
                co.moveTo(segment[0], segment[1]);
                co.arc(segment[0], segment[1], segment[2], segment[3], segment[4], 0);
            co.stroke();
            co.fill();
            
            e.stopPropagation();
        }
    }
    
    window.onclick = function (e)
    {
        RGraph.redraw();
    }
</script>

This method was formerly a common object method, called RGraph.getSegment(e), but has now (March 2011) been moved to be part of the Pie chart object.

The explodeSegment() function allows you to programmatically trigger the exploding (ie the highlighting of) a particular segment. The Explode() method is used like so:

<script>
    pie = new RGraph.Pie({
        id: 'cvs',
        data: [8,9,4,6]
    }).draw();

    pie.explodeSegment(index, size);
</script>

The index argument is the zero-indexed segment to operate on (counting from the north axis). And the size is measured in pixels.

This method can be used to get an appropriate angle for a value using the "scale" of the Pie chart. So if your Pie chart is showing values that go from 0-100 and your requested value is 50, this method will return an angle for the bottom of the Pie chart (ie half way around).

This method can be used to set an event listener on an object. It operates in a similar way to the jQuery on() function. The first argument is the event that you wish to attach to and the second is the handler function. For example:

.on('draw', function (obj)
{
    // Put event code here
});

The function is useful if you use method chaining when creating your charts:

new RGraph.Pie({
    id: 'cvs',
    data: [4,5,3,8,6,3]
}).on('draw', function (e, shape)
{
    // Put your ondraw code here
}).on('click', function (e, shape)
{
    // Handle the click event
}).draw()

The exec function is documented here.

The Horseshoe Meter

Prior to version 5.02 it was possible to get this type of meter but it involved a lot of code (which you could always have put in a library file, but still...).

But now there's a dedicated class for it so it becomes an awful lot easier to create these types of charts. The code looks like this:

<script>
    new RGraph.HorseshoeMeter({
        id: 'cvs',
        min: 0,
        max: 100,
        value: 65,
        options: {
        }
    }).roundRobin();
</script>

Animation effects

• The Grow effect (effects-pie-grow.html in the download archive)
• The Explode effect (effects-pie-explode.html in the download archive)
• The RoundRobin effect (effects-pie-roundrobin.html in the download archive)

<script>
    /**
    * Optional callback function that's called when the effect is complete
    */
    function myCallback (obj)
    {
        // ...
    }

    new RGraph.Pie({
        id: 'cvs',
        data: [8,6,6,5,3,4,2],
        options: {
        }
    }).grow({frames: 60}, myCallback)
    // .implode({frames: 60}, myCallback)
    // .roundRobin({frames: 60}, myCallback)
</script>