http://qs1969.pair.com?node_id=65726


in reply to Question about using hash indexes with GD::Graph

I still don't think that will solve the problem of the error. I would agree with jeffa on how to format your data but your 2nd to the last line I think is what is hanging you up. This is my suggestion: 

print IMG $gd->plot(\@data)->png;

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Re: Re: Question about using hash indexes with GD::Graph
by vonman (Acolyte) on Mar 20, 2001 at 20:35 UTC
    You are correct the error message that I am receiving is 
    Can't call method "png" on an undefined value at _graph_test.pl line 9
+1, <STDIN> line 1.

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Re: Re: Question about using hash indexes with GD::Graph
by vonman (Acolyte) on Mar 20, 2001 at 20:51 UTC
    I am still running into trouble with the data. I have changed the code to read like follows 
    my (@h,@c);
push @h, $_->{'hour'} foreach(@{$data});
push @c, $_->{'count'} foreach(@{$data});
my $new = [ \@h, \@c];
print (\@new);


#@data=(["1st","2nd","3rd"],
#        [9,4,7]);


#  I have a hash table with $data[$index]{'hour'} and $data[$index]{'c
+ount'}
#
$graph= GD::Graph::lines->new(400,300);
$graph->set(
    x_label => 'Hour',
    y_label => 'Transaction Volume',
    title => 'Number of transactions per hour',
    y_max_value => 20,
    y_label_skip => 1,
    y_tick_number => 1);

    #$gd = $graph->plot(\@data);

    open (IMG,'>file.png') or die $!;
    binmode IMG;
    print IMG $graph->plot(\@new)->png;

    close IMG;

    [download]
    but when I run it I still receive the same error. If I uncomment the @data lines and plot to @data instead of @new it works. Any ideas?
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[d/l]
      because $new is an array reference, so all you need to do is fill it in as $graph->plot($new)->png;
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        Still getting the same error with the follwing line as the only change. 
            print IMG $graph->plot($new)->png;

        [download]
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[d/l]
      $new is a already a reference to an array consisting of two arrayrefs. There is no such thing (yet) as @new in the code snippet you've posted. Try it with 
      print IMG $graph->plot($new)->png;

      [download]
      (instead of the \@new you have there now) and see what happens.

      use strict should have caught this. You *are* using, strict, aren't you?

      Philosophy can be made out of anything. Or less -- Jerry A. Fodor

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