I installed the module, and tried it using the bits and snippets from the module's POD, with no luck. In digging through the package's contents, though, I found 'scripts/histogram.pl', which did work. In comparing the code there with the snippets from the POD, the issue appears to be with the data. The example in the POD for the 1.0 version shows:

               $data = [1,5,7,8,9,10,11,3,3,5,5,5,7,2,2];
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              @data = (1,5,7,8,9,10,11,3,3,5,5,5,7,2,2);
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Hope that helps.

Thank You very much. The example is working. 
since i need 3 histograms, I tried using subroutine call to draw the h
+istogram chart & i am not getting the results. 

the code in main is as follows:

my $image2 = Covarion_Modules::draw_hist(\@hist);
open(IMG, '>hist.png') or die $!;
binmode IMG;
print IMG $image2->png;

and the subroutine is :

sub draw_hist{

my ($h) = @_;

use CGI ':standard';
use GD::Graph::histogram;

@data = @$h;
my $graph = new GD::Graph::histogram(400,600);

$graph->set(
                y_label         => 'Count',
                x_label         => 'Data',
                title           => 'A Histogram Chart',
                x_labels_vertical => 1,
                bar_spacing     => 0,
                shadow_depth    => 1,
                shadowclr       => 'dred',
                transparent     => 0,
        )
        or warn $graph->error;

my $image = $graph->plot(\@data) or die $graph->error;
return($image);
}


I am getting the error:

Useless use of a constant in void context at /usr/lib/perl5/site_perl/
+5.8.0/GD/Graph/histogram.pm line 203.
Use of uninitialized value in string eq at /usr/lib/perl5/site_perl/5.
+8.0/GD/Graph/histogram.pm line 42.
Argument "" isn't numeric in numeric eq (==) at /usr/lib/perl5/site_pe
+rl/5.8.0/GD/Graph/histogram.pm line 181.
Use of uninitialized value in string eq at /usr/lib/perl5/site_perl/5.
+8.0/GD/Graph/histogram.pm line 42.
Use of uninitialized value in string eq at /usr/lib/perl5/site_perl/5.
+8.0/GD/Graph/histogram.pm line 42.


any suggestions please
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I'm not sure what is causing the error you are seeing, but I can suggest the following variation that might work for you:

sub draw_graph {
    my ( $filename, @data ) = @_;
    my $graph = new GD::Graph::histogram( 400, 600 );
    $graph->set(
        x_label           => 'Data',
        y_label           => 'Count',
        title             => 'A Histogram Chart',
        x_labels_vertical => 1,
        bar_spacing       => 0,
        shadow_depth      => 1,
        shadowclr         => 'dred',
        transparent       => 0,
      )
      or warn $graph->error;

    my $gd = $graph->plot( \@data ) or die $graph->error;

    open( IMG, '>' . $filename ) or die $!;
    binmode IMG;
    print IMG $gd->png;
}
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The difference being that the graph object does not have to be passed around, since it would appear that it is only being generated and written out. To call this, you might do something like the following examples:

foreach ( 1, 5, 7, 8, 9, 10, 11, 3, 3, 5, 5, 5, 7, 2, 2 ) {
    push( @data, $_ * ( $_ + 1 ) );
}
draw_graph( 'test1.png', @data );
@data = ( 1, 5, 7, 8, 9, 10, 11, 3, 3, 5, 5, 5, 7, 2, 2 );
draw_graph( 'test2.png', @data );
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HTH.

What have you tried (code wise)? How does it not work? Error messages?

I have a large 1D array of data. I need to plot the frequency of that data in the histogram format. I did plot it using 'histogram.pl' but it is not correct.(I am getting a large rectangular box) So i tried the example given in the 'histogram.pl' , to check if the module works and it also gave the same kind of result:(:( Any suggestions