| Subject: | GD::Graph to fails when plotting graphs flatlined at '0.00' (problem in GD::Graph::axestype) |
Hi,
I think i've discovered a small 'bug' in GD::Graph::axestype
If i try and plot a graph that is flatlined at '0.00' (quotes important), i get the error:
Illegal division by zero at /home/shahsag/my_tree/links/cpan/lib/GD/Graph/axestype.pm line 1176
I've tracked the problem down to a line of code right at the begining of the _best_ends method in axestype.pm where you try and specfically deal with the case where $max and $min are equal and at zero.
Unfortunately this code doesn't seem to cover the case where $max = '0.00' and $min = '0.00'.
I attach a small test script with some comments that might make things a little clearer.
Would you be willing to produce a fix for this and release a new version of GD::Graph onto CPAN?
The version of perl i am using is 5.6.1.
The version of GD::Graph is 1.33.
The OSes that i've seen this on are: Solaris 2.6 and 8 on SPARC
fyi: The reason why i can't easily switch from using '0.00' to 0.00 is that i'm getting the graph data from another cpan module (StatsView::Graph) and it feels like a change to axestype.pm might be the neatest solution.
Sagar
#!/sbcimp/run/pd/perl/5.6.1/bin/perl
use strict;
use warnings;
use GD::Graph::lines;
my($graph, $image, $margin, @data, $filename);
$filename = "/tmp/gd_graph_axis_bug.png";
$margin = 5;
$graph = GD::Graph::lines::->new(700 ,450);
$graph->set(
x_label => 'Time (Local Time)',
y_label => 'Values',
title => "Hello World",
line_width => 1,
box_axis => 0,
x_label_skip => 30, #changed
x_label_position => 1/2,
x_labels_vertical => 1,
bgclr => "white",
transparent => 0,
t_margin => $margin,
b_margin => $margin,
l_margin => $margin,
r_margin => $margin,
);
@data = (
[ '1', '2', '3', '4', '5', ],
[ '0.00', '0.00', '0.00', '0.00', '0.00', ],
);
#
# If you change all the '0.00' to 0.00 then there is no error
# but you do get a graph where the Y axis starts from a negative number (i suppose so that the line doesn't co-incide with the x axis)
#
# See end of script for an explanation of the cause
#
$image = eval {
$graph->plot(\@data);
};
if($@ or !defined $image) {
die("PLOT FAILED: $@\n");
}
print "READY TO WRITE IMAGE: $filename\n";
open(IMG, ">", $filename) or die("Unable to open $filename : $!");
binmode IMG;
print IMG $image->png;
close IMG;
# GD::Graph::axestype : line #1149-1150
#
# if $min = 0.00, and $max = 0.00, executing the following code
#CODE: ($min, $max) = ($min) ? ($min * 0.5, $min * 1.5) : (-1,1)
#CODE: if ($max == $min);
#
# results in $min = -1, $max = 1
#
#
# if $min = '0.00', and $max = '0.00', executing the following code
#CODE: ($min, $max) = ($min) ? ($min * 0.5, $min * 1.5) : (-1,1)
#CODE: if ($max == $min);
#
# results in $min = 0, $max = 0
#
# Which later causes a division by zero error!!
#
#
# So essentially the problem is down to the fact that 0.00 and '0.00' are the same when you treat them as numbers, but not as booleans
#