ChartDirector 7.0 (Perl Edition)

Variable Width Bar Chart




This example demonstrates a bar chart with variable bar widths.

ChartDirector does not really have a bar layer for variable width bars. However, an area layer can be used to create the same effect.

The variable width bars in this example are actually 4 areas, created by 4 area layers. The data set for each area layer consists of 4 points for the 4 corners of a bar.

Source Code Listing

perldemo\varwidthbar.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; # The data for the chart my $data = [800, 600, 1000, 1400]; my $widths = [250, 500, 960, 460]; my $labels = ["Wind", "Hydro", "Coal", "Natural Gas"]; # The colors to use my $colors = [0x00aa00, 0x66aaee, 0xee6622, 0xffbb00]; # Create a XYChart object of size 500 x 350 pixels my $c = new XYChart(500, 350); # Add a title to the chart using 15pt Arial Italic font $c->addTitle("Energy Generation Breakdown", "Arial Italic", 15); # Set the plotarea at (60, 60) and of (chart_width - 90) x (chart_height - 100) in size. Use a # vertical gradient color from light blue (f9f9ff) to sky blue (aaccff) as background. Set grid # lines to white (ffffff). my $plotAreaBgColor = $c->linearGradientColor(0, 60, 0, $c->getHeight() - 40, 0xaaccff, 0xf9fcff); $c->setPlotArea(60, 60, $c->getWidth() - 90, $c->getHeight() - 100, $plotAreaBgColor, -1, -1, 0xffffff); # Add a legend box at (50, 30) using horizontal layout and transparent background. $c->addLegend(55, 30, 0)->setBackground($perlchartdir::Transparent); # Add titles to x/y axes with 10 points Arial Bold font $c->xAxis()->setTitle("Mega Watts", "Arial Bold", 10); $c->yAxis()->setTitle("Cost per MWh (dollars)", "Arial Bold", 10); # Set the x axis rounding to false, so that the x-axis will fit the data exactly $c->xAxis()->setRounding(0, 0); # In ChartDirector, there is no bar layer that can have variable bar widths, but you may create a # bar using an area layer. (A bar can be considered as the area under a rectangular outline.) So by # using a loop to create one bar per area layer, we can achieve a variable width bar chart. # starting position of current bar my $currentX = 0; for(my $i = 0; $i < scalar(@$data); ++$i) { # ending position of current bar my $nextX = $currentX + $widths->[$i]; # outline of the bar my $dataX = [$currentX, $currentX, $nextX, $nextX]; my $dataY = [0, $data->[$i], $data->[$i], 0]; # create the area layer to fill the bar my $layer = $c->addAreaLayer($dataY, $colors->[$i], $labels->[$i]); $layer->setXData($dataX); # the ending position becomes the starting position of the next bar $currentX = $nextX; } # Output the chart $c->makeChart("varwidthbar.png");