Re: Netcdf4 Compound types and Examples

> Any example you could contribute would be most welcome. They need to
> run without command line arguments, and return a 0 when everything
> runs correctly...
>
> Thanks!
>
> Ed
>
> --  
> Ed Hartnett  -- address@hidden

Okay guys, here is the "example" we are working on.  A long time ago  
we put the  World Ocean Database and the GTSPP data, all subsurface  
obs that we have or get, into the old HDF-EOS point structure. The  
way we had it structured was that each file was a 10-degree square  
with a name that contained the box number as in COADS.  The HDF-EOS  
point structure had levels that made what was a series of flat tables  
look like a hierarchy by having a link field.  So level 0 data would  
be all the box 2's  in the box 10, and the level 1 data would be the  
data with the box2 number as the link field.  This allowed you to  
search for all the data in a box2 efficiently

A downside was that the number of rows in the field had to be equal  
to the sum total of depths at which there were observations.    This  
meant that there is a huge amount of empty space.  So how might we  
improve on this - why netcdf4!  We use vlen's to deal with the  
varying number of depths and a compound data type to combine together  
the info.  Groups and (sub)-Groups provide the same structure that  
was "emulated" in the point structure.  Or at least that was what we  
thought would be a good design given netcdf4's features, but that is  
what prompted my email about examples and design - there may well be  
better ways of doing this.

However, unless I miraculously find both money and a good C  
programmer, or get Fortran wrappers to work, it will be sometime  
before it happens.

BTW, at one point I used the hdf4tohdf5 program to convert these  
files to HDF5, so they can be read using that library.  I don't know  
that the conversion worked that cleanly to use with the HDF-EOS5  
library, but it should be possible to both read and write using the  
libs that are a part of Netcdf4.  I actually had a few days to begin  
to work on this, hence the series of emails.

-Roy




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"The contents of this message do not reflect any position of the U.S.  
Government or NOAA."
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Roy Mendelssohn
Supervisory Operations Research Analyst
NOAA/NMFS
Environmental Research Division 
Southwest Fisheries Science Center
1352 Lighthouse Avenue
Pacific Grove, CA 93950-2097

e-mail: address@hidden (Note new e-mail address)
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"Old age and treachery will overcome youth and skill."