[rrd-users] Problems graphing

[Laura McCord]

Thanks for the suggestions. I'll try that and see if I can get it closer 
to working.

Thanks!
Laura

Joshua Keroes wrote:
> See below
>
> On Fri, Sep 26, 2008 at 8:05 AM, Laura McCord 
> <mccordl at southwestern.edu <mailto:mccordl at southwestern.edu>> wrote:
>
>     I have my data loaded into an array but everytime I try to graph the
>     data I get a "Can't call method "png" on an undefined value...
>
>     I am using Perl and the Graph module to produce a bar graph. Here is a
>     sample of my data and my source code. Perhaps someone will notice
>     what I
>     am doing wrong.
>
>     Thanks.
>
>
>     Here is some sample data:
>
>     Fri Sep 26 00:00:00 2008          0.1
>     Fri Sep 26 01:00:00 2008          0.0
>     Fri Sep 26 02:00:00 2008          0.1
>     Fri Sep 26 03:00:00 2008          0.1
>     Fri Sep 26 04:00:00 2008          0.2
>     Fri Sep 26 05:00:00 2008          0.1
>     Fri Sep 26 06:00:00 2008          0.2
>     Fri Sep 26 07:00:00 2008          0.1
>     Fri Sep 26 08:00:00 2008          0.2
>     Fri Sep 26 09:00:00 2008          0.2
>     Fri Sep 26 10:00:00 2008          0.2
>
>     Here is a snippet of code:
>
>
> # Got use strict; use warnings; in your code? They'll help.
>  
>
>
>            #Every Hour
>           my $res = '60';
>
>           # Start on Sep 1st
>           my $start_t = "1220227200";
>
>
> # This is really Aug 31
>
>
>           my $start_t_res = int($start_t/$res)*$res;
>
>
> # And if you start to --start from this time, then you've just 
> overflowed time_t and you're trying to start at Wed Dec 31 15:59:59 
> 1969, or time 0.
>  
>
>
>           #End on Today's Date
>           my $end_t = "(int($start_t/$res)*$res)";
>
>
> # unused. But you don't want to quote it anyway. That won't work.
>  
>
>
>           my ($start,$step,$names,$data) =
>     RRDs::fetch("stats.rrd","AVERAGE","-r","$res","-s",
>     "$start_t_res","-e","now");
>
>
> # see above about starting at wrong time.
>
>
>
>           print "Start:       ", scalar localtime($start), " ($start)\n";
>            print "Step size:   $step seconds\n";
>            print "DS names:    ", join (", ", @$names)."\n";
>            print "Data points: ", $#$data + 1, "\n";
>
>
> # Try scalar @data here instead. 
>
> # Consider renaming @array1 to @timestamps and @array2 to @values or
> # better: @whatever_those_values_actually_are. That makes it easier for
> # us to read your code.
> #
> # There are faster ways to do this, but if it works, then I'll skip 
> over it for the most part.
> # The only point I'll make is that if there are multiple DS's in your 
> RRD, then you'll
> # only see the last one because the inner foreach loop will overwrite 
> all of the prior
> # values in @line with just the last.
> #
>
>            print "Data:\n";
>            foreach my $line (@$data) {
>                   $start += $step;
>                   $min++;
>                      #Here I am only loading hourly data into the array
>                      if($min == 60){
>                            $array1[$i] = localtime($start);
>                              foreach my $val (@$line) {
>                                   $array2[$i] = $val;
>                               }
>                            $i++;
>                            $min=0;
>                      }
>            }
>
>           for($i=0;$i < @array1; $i++){
>                   print $array1[$i]." ";
>                   printf "%12.1f ", $array2[$i];
>                   print "\n";
>           }
>
>
> # I prefer something like this here:
> #
> # for my $i (0..$#timestamps) {
> #     printf "$timestamps[$i]: %12.1f\n", $values[$i];
> # }
>
>           @actualdata = (\@array1,\@array2);
>
>
> # Let's comment the above line out and ...
>  
>
>
>           my $graph = new GD::Graph::bars;
>            $graph->set(
>               x_label         => 'Date/Time',
>               y_label         => 'Messages',
>               title           => 'Dropped Messages',
>               y_max_value     => 10,
>               y_tick_number   => 1,
>               y_label_skip    => 1,
>
>               # shadows
>               bar_spacing     => 10,
>               shadow_depth    => 4,
>               shadowclr       => 'dred',
>
>               transparent     => 0,
>           ) or warn $graph->error; 
>
>
>           my $image = $graph->plot(\@actualdata)->png();
>
> # ...move it down here where it's a little closer to the action thusly:
> #
> # my $image = $graph->plot( [\@timestamps, \@values] )->png;
>
> Maybe that'll get you a little closer.
>
> Good luck,
> Joshua
>