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Canvas Pie chart API reference

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

• Example
• Properties
• Methods
• Animation effects

Example

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

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

The example pages are here.

Properties

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

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

• Chart configuration
• Margins
• Colors
• Labels and text
• Titles
• Shadow
• Interactive features
• Key
• Zoom
• Events
• Miscellaneous

Chart configuration

Margins

Colors

Labels and text

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

Titles

Shadow

Interactive features

Key

Zoom

Events

Miscellaneous

Methods

• 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 (6th March 2011) been moved to be part of the Pie chart object.

The explodeSegment() method 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-index segment to operate on (counting from the north axis). An 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 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:

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

The exec function is documented here.

Animation Effects

• Grow effect
• Explode effect
• RoundRobin effect

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

    var 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>