Perl Cd Bookshelf [Electronic resources] نسخه متنی

15.18. Graphing Data

You
have numerical data that you want to represent as a bar, pie, or line
chart.

15.18.2. Solution

Use the
GD::Graph::* modules from CPAN:

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
# ...
];

15.18.3. Discussion

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)

---

15.17. Removing the DOS Shell Window with Windows Perl/Tk		15.19. Thumbnailing Images

---

Copyright © 2003 O'Reilly & Associates. All rights reserved.