ChartDirector Ver 4.1 (PHP Edition Edition)

Y-Axis Scaling

This example demonstrates how to control auto-scaling.
By default, ChartDirector auto-scales all axes. The Axis.setAutoScale method controls the top extension, bottom extension and the zero affinity parameters that ChartDirector uses during auto-scaling. The first two parameters determine the amount of top and bottom margins to reserve during auto-scaling, while the last parameter determines when the axis should start from the origin (0).
The first 3 charts demonstrate the effects of different top/bottom extensions.
The 4th chart demonstrates that one could exclude a segment on the ends of an axis from scaling using Axis.setMargin.
The 5th chart demonstrates manual scaling instead of auto-scaling. In manual scaling, the axis scale is explicitly provided by using Axis.setLinearScale, Axis.setLinearScale2, Axis.setLogScale, Axis.setLogScale2, Axis.setDateScale or Axis.setDateScale2.

Source Code Listing

[File: phpdemo/axisscale.php]

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

    # The data for the chart
    $data = array(5.5, 3.5, -3.7, 1.7, -1.4, 3.3);
    $labels = array("Jan", "Feb", "Mar", "Apr", "May", "Jun");

    # Create a XYChart object of size 200 x 180 pixels
    $c = new XYChart(200, 180);

    # Set the plot area at (30, 20) and of size 140 x 130 pixels
    $c->setPlotArea(30, 20, 140, 130);

    # Configure the axis as according to the input parameter
    if ($_REQUEST["img"] == "0") {
        $c->addTitle("No Axis Extension", "arial.ttf", 8);
    } else if ($_REQUEST["img"] == "1") {
        $c->addTitle("Top/Bottom Extensions = 0/0", "arial.ttf", 8);
        # Reserve 20% margin at top of plot area when auto-scaling
        $c->yAxis->setAutoScale(0, 0);
    } else if ($_REQUEST["img"] == "2") {
        $c->addTitle("Top/Bottom Extensions = 0.2/0.2", "arial.ttf", 8);
        # Reserve 20% margin at top and bottom of plot area when auto-scaling
        $c->yAxis->setAutoScale(0.2, 0.2);
    } else if ($_REQUEST["img"] == "3") {
        $c->addTitle("Axis Top Margin = 15", "arial.ttf", 8);
        # Reserve 15 pixels at top of plot area
        $c->yAxis->setMargin(15);
    } else {
        $c->addTitle("Manual Scale -5 to 10", "arial.ttf", 8);
        # Set the y axis to scale from -5 to 10, with ticks every 5 units
        $c->yAxis->setLinearScale(-5, 10, 5);
    }

    # 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.
    $barLayerObj = $c->addBarLayer3($data);
    $barLayerObj->setBorderColor(-1, 1);

    # output the chart
    header("Content-type: image/png");
    print($c->makeChart2(PNG));
    ?>

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