Hm... I've gotten this to sort-of work, but the x-data is not spaced properly (the dates are not all equidistant, but are shown as such on the plot). In fact, the docs say as much:
"First of all: GD::Graph does not support numerical x axis the way it should. Data for X axes should be equally spaced. That understood: There is some support to make the printing of graphs with numerical X axis values a bit better, thanks to Scott Prahl."
Here's the code:
#!/usr/bin/env perl
use Modern::Perl;
use DateTime;
use GD::Graph::points;
my @x_vals = (
'2012-11-07',
'2012-11-08',
'2012-11-15',
'2012-11-19',
'2012-11-30',
);
my @y_vals = (
11, 12, 13, 14, 15,
);
# -------------------------------------------
my @epoch_x_vals = ();
for my $d (@x_vals) {
my ($y, $m, $d) = split /-/, $d;
push @epoch_x_vals,
DateTime->new(year => $y,
month => $m,
day => $d)
->epoch;
}
my @data = (\@epoch_x_vals, \@y_vals);
sub x_number_formatter {
my ($e) = @_;
my $dt = DateTime->from_epoch(epoch => $e);
return $dt->ymd;
}
my $graph = GD::Graph::points->new(400, 300);
$graph->set(
x_label => 'X label',
x_labels_vertical => 1,
x_tick_number => 10, # experimented with this value a bit
x_number_format => \&x_number_formatter,
y_label => 'Y label',
title => 'some title',
) or die $graph->error;
my $gd = $graph->plot(\@data) or die $graph->error;
open(my $img, '> plot.png') or die $!;
binmode $img;
print $img $gd->png;
Will do some experimenting with gnuplot to see what I can get.