http://qs1969.pair.com?node_id=82801

chinman has asked for the wisdom of the Perl Monks concerning the following question:

Hey, I'm in need of some Monk wisdom. I've been dorking around with GD::Graph to try to plot an x,y line graph with lots o' points (>1000). I've got the basics working fine. Well, I'd like to label the maxima, or maybe the 10 biggest y values by using the show_values option. The problem is if I turn labeling on with my "thousand points of light" I've got way too many data point labels and everything runs together. I'm wondering if anyone knows a way to label just a few without blowing away the rest of the points. I've tried using the $data->copy method, followed by setting values to undefined but that does not appear to do what I want. It seems like when you say show_values it always wants to show_values for all data points. Thanks in advance for the help!

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Re: GD::Graph labeling
by Prof Avery (Novice) on May 25, 2001 at 03:44 UTC
    Try using values_format, formatting the maxima as numbers and everything else as an empty string, e.g. 
    sub v_format {
  my $value = shift;

  if ($value >= ($MAX - $EPSILON)) {
    return $value
  } else {
    return '';
}

$my_graph->set('values_format' => \&v_format);

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[d/l]
      Prof Avery,

      Thanks, that was a huge help! Somehow, values_format did not come up on my radar screen.

      Regards,

      chinman

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Re: GD::Graph labeling
by ryddler (Monk) on May 24, 2001 at 18:14 UTC
    If I'm reading your post correctly, take a look at these values in the docs for GD::Graph 
    x_label_skip, y_label_skip

Print every x_label_skipth number under the tick on the
x axis, and every y_label_skipth number next to the tick
on the y axis. Default: 1 for both.

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    Update:
    I misread this question, but the settings I pointed out above are still useful for some graphing ops, so I'll leave the post intact.

    ryddler
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[d/l]
      ryddler, Thanks for your post. Yeah, what I'm looking to do is label certain points on the graph (like the maximum Y values). I've got the tic labeling figured out. While I'm on this topic...are there any monk recommendations for another graphing module that do a better job at what I'm trying to do? Basically, I'm taking spectra which contain thousands of x, y data points and I just want to do some automated labeling of some of the biggest peaks. Thanks... chinman
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