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Recipe: Matlab program as OPeNDAP client: Difference between revisions

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By accessing the collection <code>inst01hr_3d_T_Cv</code> via the OPeNDAP server
By accessing the collection <code>inst01hr_3d_T_Cv</code> via the OPeNDAP server
  http://opendap.nccs.nasa.gov/dods/OSSE/G5NR/Ganymed/7km
  https://opendap.nccs.nasa.gov/dods/OSSE/G5NR/Ganymed/7km


we want to read the surface temperature data inside the box bound by latitudes 25<sup>o</sup>N, 50<sup>o</sup>N and longitudes -130<sup>o</sup>W, -65<sup>o</sup>W for 2006/Sep/18, 9z and compute its min/max.
we want to read the surface temperature data inside the box bound by latitudes 25<sup>o</sup>N, 50<sup>o</sup>N and longitudes -130<sup>o</sup>W, -65<sup>o</sup>W for 2006/Sep/18, 9z and compute its min/max.
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The metadata for the collection <code>inst01hr_3d_T_Cv</code> is available at
The metadata for the collection <code>inst01hr_3d_T_Cv</code> is available at
  http://opendap.nccs.nasa.gov/dods/OSSE/G5NR/Ganymed/7km/0.5000_deg/inst/inst01hr_3d_T_Cv.info
  https://opendap.nccs.nasa.gov/dods/OSSE/G5NR/Ganymed/7km/0.5000_deg/inst/inst01hr_3d_T_Cv.info


==== Code ====
==== Code ====
This code accesses the collection <code>inst01hr_3d_T_Cv</code> from the OPeNDAP server and reads a subset of the temperature data.
This code accesses the collection <code>inst01hr_3d_T_Cv</code> from the OPeNDAP server and reads a subset of the temperature data (all levels inside the bounding box specified above) and computes its max/min. It then computes the max/min of the above data at the surface (level=72).


NOTE:
NOTE:
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<syntaxhighlight lang="matlab" line>
<syntaxhighlight lang="matlab" line>
% opendap url
% opendap url
opdurl = 'http://opendap.nccs.nasa.gov:9090/dods/OSSE/G5NR/Ganymed/7km/0.5000_deg/inst/inst01hr_3d_T_Cv'
opdurl = 'https://opendap.nccs.nasa.gov:9090/dods/OSSE/G5NR/Ganymed/7km/0.5000_deg/inst/inst01hr_3d_T_Cv'


% bounding box
% bounding box
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</syntaxhighlight>
</syntaxhighlight>


==== Compile and link ====
==== Output ====
Running this MATLAB script, we get the output


We use the utility <code>nf-config</code> (included in the NetCDF-4 installation) to identify the linking rules
>> g5nr_reader
 
For a typical NetCDF-4 installation, the above code, <code>g5nr_reader_dap.f90</code> can be compiled and linked to the NetCDF-4 library via
opdurl =
  gfortran -o g5nr_reader_dap.x `nf-config --fflags` g5nr_reader_dap.f90 `nf-config --flibs`
 
  https://opendap.nccs.nasa.gov:9090/dods/OSSE/G5NR/Ganymed/7km/0.5000_deg/inst/inst01hr_3d_T_Cv
creating the executable <code>g5nr_reader_dap.x</code>.
   
 
  Reading Tsub (subset of T)...done.
NOTE:
  max(Tsub): 305.604828
# You can use your favorite Fortran compiler instead of <code>gfortran</code>.
min(Tsub): 191.695648
# If the NetCDF-4 library was built with parallel I/O support, you will need to use <code>mpif90</code> to link, even if your code does not use the MPI library.
max(Tsub at surface): 305.604828
 
min(Tsub at surface): 276.292328
==== Run ====
Running the executable,
 
  ./g5nr_reader_dap.x
 
produces the output
  Reading T (subset)...
  T (subset):   305.6048      191.6956


== Discussion ==
== Discussion ==
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