ChartDirector Ver 3.0 (Perl 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: perldemo/axisscale.pl] (The CGI version is available as "perldemo_cgi/axisscale.pl".)
#!/usr/bin/perl use perlchartdir; sub createChart { my $img = shift; #The data for the chart my $data = [5.5, 3.5, -3.7, 1.7, -1.4, 3.3]; my $labels = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"]; #Create a XYChart object of size 200 x 180 pixels my $c = new XYChart(200, 180); #Set the plot area at (30, 20) and of size 140 x 130 pixels $c->setPlotArea(30, 20, 140, 130); #Configure the axis as according to the input parameter if ($img == "0") { $c->addTitle("No Axis Extension", "arial.ttf", 8); } elsif ($img == "1") { $c->addTitle("Top/Bottom Extensions = 0/0", "arial.ttf", 8); #Reserve 20% margin at top of plot area when auto-scaling $c->yAxis()->setAutoScale(0, 0); } elsif ($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 $c->yAxis()->setAutoScale(0.2, 0.2); } elsif ($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. $c->addBarLayer3($data)->setBorderColor(-1, 1); #output the chart $c->makeChart("axisscale$img.png") } createChart(0); createChart(1); createChart(2); createChart(3); createChart(4);