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Can I modify the scripts Ferret uses to generate output?
Here an alternate visualization script was used that plots data sampling locations over a data product generated by objective analysis.
LAS data providers can associate custom scripts with a dataset or variable by adding properties to the XML configuration file. Two script related properties include the init_script property and the script_prefix property.
Script related properties are specified in the .xml files in the same manner as other properties:
<properties> <ferret> <init_script>define_aco2</init_script> <script_prefix>co2_survey_</script_prefix> </ferret> </properties>
The initialization script, define_aco2.jnl in this case, should reside in the server/jnls directory and can be used to create virtual variables from other variables in the dataset.
The script prefix, "co2_survey_" above, is prepended to the "std_" template or journal files when LAS requests output. In our case, a request for a plot will use the template file co2_survey_std_gif.tmpl to generate a sequence of commands to Ferret. A request for data would call co2_survey_std_list.jnl.
The server code (server/Ferret.pl) uses the following algorithm to decide which script to use:
# 1) look for template file with script prefix
# 2) look for template file without script prefix
# 3) look for journal file with script prefix
# 4) look for journal file without script prefix
For plots not using templates, <view>ref is tacked on to maintain backwards compatibility.
So, if you request an XY plot of a variable with a script_prefix named "foo_", the server would look for:
Jonathan Callahan: Jonathan.S.Callahan@noaa.gov
Last modified: September 19, 2000