ChartDirector 7.0 (Perl 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

perldemo\axisscale.pl
#!/usr/bin/perl # The ChartDirector for Perl module is assumed to be in "../lib" use File::Basename; use lib (dirname($0)."/../lib") =~ /(.*)/; use perlchartdir; sub createChart { my $chartIndex = 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 190 pixels my $c = new XYChart(200, 190); # Set the plot area at (30, 20) and of size 140 x 140 pixels $c->setPlotArea(30, 20, 140, 140); # Configure the axis as according to the input parameter if ($chartIndex == 0) { $c->addTitle("No Axis Extension", "Arial", 8); } elsif ($chartIndex == 1) { $c->addTitle("Top/Bottom Extensions = 0/0", "Arial", 8); # Reserve 20% margin at top of plot area when auto-scaling $c->yAxis()->setAutoScale(0, 0); } elsif ($chartIndex == 2) { $c->addTitle("Top/Bottom Extensions = 0.2/0.2", "Arial", 8); # Reserve 20% margin at top and bottom of plot area when auto-scaling $c->yAxis()->setAutoScale(0.2, 0.2); } elsif ($chartIndex == 3) { $c->addTitle("Axis Top Margin = 15", "Arial", 8); # Reserve 15 pixels at top of plot area $c->yAxis()->setMargin(15); } else { $c->addTitle("Manual Scale -5 to 10", "Arial", 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 $c->makeChart("axisscale$chartIndex.png"); } createChart(0); createChart(1); createChart(2); createChart(3); createChart(4);