Dear Monks,

I've been messing around with GD::Graph for a while as an option for dynamically serving up some graphs via a CGI script. For the most part I'm happy, it runs pretty fast and gives me pretty pictures. I have encountered some strange behavior with data running off the graph... for simplicity, here is an example of a very basic graph that works normally:

use strict;
use GD::Graph::lines;

my @data = ( [1, 2, 3, 4, 5, 6, 7, 8, 9,],
         [ 8, 8.25, 8.5, 8.35, 8.76, 8.21, 8.6, 8.8, 8.5],
         [ 7.4, 7.6, 7.8, 7.9, 7.4, 8.5, 7, 7.87, 8.34],
         [ 4, 5, 6, 5.6, 5.5, 6.1, 6.3, 5.2, 5.6]);

my $graph = new GD::Graph::lines (600, 400);

$graph->set(
    title => "Blah, Blah, Blah",
    x_label => 'X axis label',
    y_label => 'Y axis label',
    boxclr => '#C0C0C0'
);

## Next code snippet goes here

$graph->set_legend("data set 1", "data set 2", "data set 3");

print "Content-type: image/png\n\n";
binmode(STDOUT);
print $graph->plot(\@data)->png();
[download]

Now lets say you want to allow the user to "zoom in" on an area of the graph. Pretend that after some CGI magic and some passed parameters, the min/max for the x and y axes are as follows and you insert this code where I have marked in the above script:

$graph->set(
    y_min_value => 6,
    y_max_value => 10,
    x_min_value => 3,    
    x_max_value => 7
);
[download]

The lines run off the edge of the x and y axes, the x_max_value does not appear to be properly set, etc. Am I dumb and have an error in the code somewhere or do you folks encounter the same problem? Could be a better looking graph, eh? Didn't find a fix for this in the documentation. So far it does this on my Linuxbox (forgot what flavor, I don't manage it), and a WinNT machine, both with what I think is the most recent module of GD::Graph. If this is a known problem and there is a fix, do let me know.

I understand I could modify my data sets so that the data "fits" within the plotting area. But, I'm lazy and I feel like this is something GD::Graph should be able to handle internally. Any wisdom you may offer will be much appreciated.

Thank you,
-C