15.18. Graphing Data
use GD::Graph::lines; # bars, lines, points, pie $chart = GD::Graph::lines->new(480,320); $chart->set(x_label => $X_AXIS_LABEL, # no axes for pie chart y_label => $Y_AXIS_LABEL, title => $GRAPH_TITLE, # ... more options possible ); $plot = $chart->plot($DATA_REF) or die $chart->error; # do something with $plot->png which is the image in PNG form
Here is a sample data structure (every row must have the same number of values):
$DATA_REF = [ [ 1990, 1992, 1993, 1995, 2002 ], # X values [ 10, 15, 18, 20, 25 ], # first dataset [ 9, undef,17, undef,12 ], # second dataset # ... ];
The GD::Graph module requires you to have the GD module installed, which itself depends on a C library available from http://www.boutell.com/gd/. Early versions of this library created GIF images, but since the owners of the GIF patent are cracking down, the library now emits PNG and JPEG images:
$png_data = $plot->png; $jpg_data = $plot->jpeg;
The documentation for GD::Graph lists a large number of options you can fine-tune (colors, fonts, placement), but the most important ones are labels and the image title. There are no axes to label in pie charts, so the x_label and y_label options are not available. By default, pie charts are drawn with a pseudo-3D look, which you can disable by setting the 3d option to a false value.
Recipe 15.23 contains a program that (crudely) extracts the day of the week on which each mail message in a mailbox was sent, and then graphs that data.
15.18.4. See Also
Documentation for the GD and GD::Graph modules; Perl Graphics Programming, by Shawn Wallace (O'Reilly)
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