ChartDirector Ver 3.1 (PHP Edition Edition)

Y-Axis Scaling


        

This example illustrates how to control scaling of an axis.

By default, ChartDirector will auto-scaled 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 three charts demonstrates the effects of different top/bottom extensions. (Please refer to Axis.setAutoScale on what these parameters mean.)

The fourth chart demonstrates that one could exclude a segment on the ends of an axis from scaling using Axis.setMargin.

The fifth chart demonstrates using manual scaling instead of auto-scaling. A manual linear scale can be configured using Axis.setLinearScale or Axis.setLinearScale2. ChartDirector also supports Axis.setLogScale, Axis.setLogScale2, Axis.setDateScale and Axis.setDateScale2 for configuring manual log and date scales.

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 $c->setPlotArea(30, 20, 140, 130); #Configure the axis as according to the input parameter if ($HTTP_GET_VARS["img"] == "0") { $c->addTitle("No Axis Extension", "arial.ttf", 8); } else if ($HTTP_GET_VARS["img"] == "1") { $c->addTitle("Top/Bottom Extensions = 0/0", "arial.ttf", 8); #Reserve 20% margin at top of plot area when auto-scaling $c->yAxis->setAutoScale(0, 0); } else if ($HTTP_GET_VARS["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 $c->yAxis->setAutoScale(0.2, 0.2); } else if ($HTTP_GET_VARS["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. $barLayer3Obj = $c->addBarLayer3($data); $barLayer3Obj->setBorderColor(-1, 1); #output the chart header("Content-type: image/png"); print($c->makeChart2(PNG)); ?>