Tick Density

This example demonstrates how to control the axis tick density in auto-scaling.

By default, in auto-scaling, ChartDirector automatically chooses the tick spacing for the axis.

In some cases, you may want to suggest the tick spacing to use. This can be done by using Axis.setTickDensity.

Note that the actual tick spacing chosen by ChartDirector may not be equal to the suggested tick spacing. The suggested tick spacing is only a lower bound. It is because there may be other constraints when choosing the ticks. For example, the tick positions should be "neat numbers", such as (0, 5, 10, ...), and not arbitrary numbers like (0, 4.792, 9.584, ...). Also, by default, the axis starts and ends at tick positions (configurable using Axis.setRounding), which means the axis length must be divisible by the tick spacing. These and other constraints will affect the exact ticks being chosen.

In this example, one of the charts is drawn using the default tick spacing. The other chart is drawn using a suggested tick spacing of 10 pixels. Note that the actual tick spacing is slightly larger than 10 pixels.

[File: phpdemo/ticks.php]

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

function createChart($viewer, $chartIndex)
{
    # The data for the chart
    $data = array(100, 125, 265, 147, 67, 105);
    $labels = array("Jan", "Feb", "Mar", "Apr", "May", "Jun");

    # Create a XYChart object of size 250 x 250 pixels
    $c = new XYChart(250, 250);

    # Set the plot area at (27, 25) and of size 200 x 200 pixels
    $c->setPlotArea(27, 25, 200, 200);

    if ($chartIndex == 1) {
        # High tick density, uses 10 pixels as tick spacing
        $c->addTitle("Tick Density = 10 pixels");
        $c->yAxis->setTickDensity(10);
    } else {
        # Normal tick density, just use the default setting
        $c->addTitle("Default Tick Density");
    }

    # Set the labels on the x axis
    $c->xAxis->setLabels($labels);

    # Add a color bar layer using the given data. Use a 1 pixel 3D border for the bars.
    $c->addBarLayer3($data)->setBorderColor(-1, 1);

    # Output the chart
    $viewer->setChart($c, SVG);

    # Include tool tip for the chart
    $viewer->setImageMap($c->getHTMLImageMap("", "", "title='Revenue for {xLabel}: US\${value}M'"));
}

# This example includes 2 charts
$viewers = array();
for ($i = 0; $i < 2; ++$i) {
    $viewers[$i] = new WebChartViewer("chart$i");
    createChart($viewers[$i], $i);
}
?>

<!DOCTYPE html>
<html>
<head>
    <title>Tick Density</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;">
        Tick Density
    </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 are the chart images ****** -->
    <?php
        for ($i = 0; $i < count($viewers); ++$i) {
            echo $viewers[$i]->renderHTML(), " ";
        }
    ?>
</body>
</html>