Caro-COOPS Bulletin Board

[jcothran]

Note: In my graphing experience I started with php 'jpgraph', moved to the below described perl GD::Graph package, and have since moved to gnuplot which is (I hope) the final solution for what our graphing needs currently are. Gnuplot's main advantage is that it separates the axis definition from the data itself, both of the earlier graphing packages have a weakness in that the x-axis is dependent on the data plotted - which means that if you're using the x-axis as the time dimension, when the data might be sampled irregularly, the graph doesn't visually represent this correctly. The data-axis dependency also becomes an issue when you might want to represent several stations with different time sampling intervals within the same graph.

I've added documentation on using gnuplot( which is what I'd recommend over the below documentation at http://caro-coops.org/bb/viewtopic.php?t=330 ).

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The attached code(graphs.tar) uses the perl GD::Graph module http://search.cpan.org/~mverb/GDGraph-1.43/Graph.pm to create a basic graph for one to many(say 12) graphs against a given variable.

The code also requires the GD::Text module installed as well.

After unzipping, you should be able to run

perl graphMulti.pl

to produce the attached graph. graphMulti.pl is just a sample code file which populated the arguments for the call to my_graph($graph_data, $station_id, $title, $y_units, $y_range_min, $y_range_max, $dir_path) located in graphMulti.lib which does the graphing work.

Thanks to Gomoos (www.gomoos.org) for sharing their code showing how they use GD::Graph in practice on their website.