[rrd-users] be more selective with datasources to plot

[Alceu R. de Freitas Jr.]

Greetings,
I'm creating a rrdtool database with a large number of datasources (~45). It is working fine, but due the large number of datasources, it's pretty hard to make find out which line is which datasource based on the legend since I'm forced to used small intervals of color to make them different to the eyes.
Just to illustrate, I used an array to fetch a color for each line (hope it is OK to put Perl code here):
    my @colors = (
        '000080', '0000CD', '006400', '008080', '00BFFF', '00FA9A',
        '00FF7F', '00FFFF', '1E90FF', '228B22', '2F4F4F', '3CB371',
        '4169E1', '483D8B', '4B0082', '5F9EA0', '66CDAA', '6A5ACD',
        '708090', '7B68EE', '7FFF00', '800000', '808000', '87CEEB',
        '8A2BE2', '8B008B', '8FBC8F', '9370DB', '98FB98', '9ACD32',
        'A52A2A', 'ADD8E6', 'AFEEEE', 'B0E0E6', 'B8860B', 'BC8F8F',
        'C0C0C0', 'CD5C5C', 'D2691E', 'D3D3D3', 'DA70D6', 'DB7093',
        'DCDCDC', 'DEB887', 'E6E6FA', 'EE82EE', 'F08080', 'F0F8FF',
        'F0FFFF', 'F5DEB3', 'F5F5F5', 'F8F8FF', 'FAEBD7', 'FAFAD2',
    );

In most of cases, only part of those datasources will have interesting results (~8% of datasources will have values near zero). I would like to filter only the datasources that have a value greater than a threshold.
My naive attempt was to use fetch with the same values I'll be using for graph (start date, end date an cfunc).
Is this procedure correct? Is there a better way to do that?
Thanks,
Alceu

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