#! perl -slw
use strict;
use GD::Graph::lines;

my @logConc = 1 .. 50;
my @data = map{ -3 + rand( 6 ) } 1 .. 50;

my @graphs = map GD::Graph::lines->new(500,300, 1), 1..2;

for ( @graphs ) {
    $_->set(
        x_label         =>  'Logged stuff',
        y_label         =>  'Intensity',
        title           =>  "Plot of stuff",
        line_width      =>  1,
        legend_spacing  =>  5,
        x_tick_number   =>  'auto',
        box_axis        =>  0,
        y_min_value     =>  -2,
        y_max_value     =>  2,
        transparent     =>  0
    ) or die $_->error;
    $_->set_legend('legend');
}

## Draw the full graph
my $gd1 = $graphs[ 0 ]->plot( [ \@logConc, \@data ] )
 or die $graphs[0]->error;

## Draw another with the same size and options, but null data.
my $gd2 = $graphs[ 1 ]->plot([[0],[0]]);

## Copy the relevant portion of the full graph over the empty one
$gd2->copy( $gd1, 0, 20, 0, 20, 500, 230 );

## And display the latter.
open PNG, '>:raw', 'junk.png';
print PNG $gd2->png();
close PNG;
system 'junk.png';