Polar Bubble Chart

This example demonstrates how to create polar bubble charts. It also demonstrates using alternating background colors along the radial direction.

A polar bubble chart can be created as a polar line chart with circles as data symbols. The line width is set to 0, so only the symbols can be seen. The symbol sizes are then controlled using another data series. This will create the effects of a bubble chart.

The detail steps are:

Create a polar line layer using PolarChart.addLineLayer.
Enable data symbols for the line using PolarLayer.setDataSymbol (or PolarLayer.setDataSymbol2 or PolarLayer.setDataSymbol3 or PolarLayer.setDataSymbol4). ChartDirector supports using arbitrary shapes as bubbles, although traditionally, circles are used.
Disable the line by setting its width to 0 using PolarLayer.setLineWidth.
Control the size of the symbols by a data series using PolarLayer.setSymbolScale.

Note that in this example, the polar plot area uses two alternating background colors along the radial direction. This is by using PolarChart.setPlotAreaBg.

[File: phpdemo/polarbubble.php]

<?php
require_once("../lib/phpchartdir.php");

# The data for the chart
$data0 = array(6, 12.5, 18.2, 15);
$angles0 = array(45, 96, 169, 258);
$size0 = array(41, 105, 12, 20);

$data1 = array(18, 16, 11, 14);
$angles1 = array(30, 210, 240, 310);
$size1 = array(30, 45, 12, 90);

# Create a PolarChart object of size 460 x 460 pixels
$c = new PolarChart(460, 460);

# Add a title to the chart at the top left corner using 15pt Arial Bold Italic font
$c->addTitle2(TopLeft, "<*underline=2*>EM Field Strength", "Arial Bold Italic", 15);

# Set center of plot area at (230, 240) with radius 180 pixels
$c->setPlotArea(230, 240, 180);

# Use alternative light grey/dark grey circular background color
$c->setPlotAreaBg(0xdddddd, 0xeeeeee);

# Set the grid style to circular grid
$c->setGridStyle(false);

# Add a legend box at the top right corner of the chart using 9pt Arial Bold font
$c->addLegend(459, 0, true, "Arial Bold", 9)->setAlignment(TopRight);

# Set angular axis as 0 - 360, with a spoke every 30 units
$c->angularAxis->setLinearScale(0, 360, 30);

# Set the radial axis label format
$c->radialAxis->setLabelFormat("{value} km");

# Add a blue (0x9999ff) line layer to the chart using (data0, angle0)
$layer0 = $c->addLineLayer($data0, 0x9999ff, "Cold Spot");
$layer0->setAngles($angles0);

# Disable the line by setting its width to 0, so only the symbols are visible
$layer0->setLineWidth(0);

# Use a circular data point symbol
$layer0->setDataSymbol(CircleSymbol, 11);

# Modulate the symbol size by size0 to produce a bubble chart effect
$layer0->setSymbolScale($size0);

# Add a red (0xff9999) line layer to the chart using (data1, angle1)
$layer1 = $c->addLineLayer($data1, 0xff9999, "Hot Spot");
$layer1->setAngles($angles1);

# Disable the line by setting its width to 0, so only the symbols are visible
$layer1->setLineWidth(0);

# Use a circular data point symbol
$layer1->setDataSymbol(CircleSymbol, 11);

# Modulate the symbol size by size1 to produce a bubble chart effect
$layer1->setSymbolScale($size1);

# Output the chart
$viewer = new WebChartViewer("chart1");
$viewer->setChart($c, SVG);

# Include tool tip for the chart
$viewer->setImageMap($c->getHTMLImageMap("", "",
    "title='{dataSetName} at ({value} km, {angle} deg)\nStrength = {z} Watt'"));
?>

<!DOCTYPE html>
<html>
<head>
    <title>Polar Bubble Chart</title>
    <!-- Include ChartDirector Javascript Library to support chart interactions -->
    <script type="text/javascript" src="cdjcv.js"></script>
</head>
<body style="margin:5px 0px 0px 5px">
    <div style="font:bold 18pt verdana;">
        Polar Bubble Chart
    </div>
    <hr style="border:solid 1px #000080; background:#000080" />
    <div style="font:10pt verdana; margin-bottom:1.5em">
        <a href="viewsource.php?file=<?=basename(__FILE__)?>">View Chart Source Code</a>
    </div>
    <!-- ****** Here is the chart image ****** -->
    <?php echo $viewer->renderHTML(); ?>
</body>
</html>