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/* This is part of the netCDF package.
Copyright 2006 University Corporation for Atmospheric Research/Unidata.
See COPYRIGHT file for conditions of use.
This is an example program which writes some 4D pressure and
temperatures. This example demonstrates the netCDF C++ API.
This is part of the netCDF tutorial:
http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-tutorial
Full documentation of the netCDF C++ API can be found at:
http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-cxx
$Id: pres_temp_4D_wr.cpp,v 1.11 2007/01/19 12:52:13 ed Exp $
*/
#include <iostream>
#include <netcdfcpp.h>
using namespace std;
// We are writing 4D data, a 2 x 6 x 12 lvl-lat-lon grid, with 2
// timesteps of data.
static const int NLVL = 2;
static const int NLAT = 6;
static const int NLON = 12;
static const int NREC = 2;
// These are used to construct some example data.
static const float SAMPLE_PRESSURE = 900.0;
static const float SAMPLE_TEMP = 9.0;
static const float START_LAT = 25.0;
static const float START_LON = -125.0;
// Return this code to the OS in case of failure.
static const int NC_ERR = 2;
int main()
{
// These arrays will store the latitude and longitude values.
float lats[NLAT],lons[NLON];
// These arrays will hold the data we will write out. We will
// only need enough space to hold one timestep of data; one record.
float pres_out[NLVL][NLAT][NLON];
float temp_out[NLVL][NLAT][NLON];
int i = 0;
// Create some pretend data. If this wasn't an example program, we
// would have some real data to write for example, model output.
for (int lat = 0; lat < NLAT; lat++)
lats[lat] = START_LAT + 5. * lat;
for (int lon = 0; lon < NLON; lon++)
lons[lon] = START_LON + 5. * lon;
for (int lvl = 0; lvl < NLVL; lvl++)
for (int lat = 0; lat < NLAT; lat++)
for (int lon = 0; lon < NLON; lon++)
{
pres_out[lvl][lat][lon] = SAMPLE_PRESSURE + i;
temp_out[lvl][lat][lon] = SAMPLE_TEMP + i++;
}
// Change the error behavior of the netCDF C++ API by creating an
// NcError object. Until it is destroyed, this NcError object will
// ensure that the netCDF C++ API returns error codes on any
// failure, prints an error message, and leaves any other error
// handling to the calling program. In the case of this example, we
// just exit with an NC_ERR error code.
NcError err(NcError::verbose_nonfatal);
// Create the file.
NcFile dataFile("pres_temp_4D.nc", NcFile::Replace);
// Check to see if the file was created.
if(!dataFile.is_valid())
return NC_ERR;
// Define the dimensions. NetCDF will hand back an ncDim object for
// each.
NcDim *lvlDim, *latDim, *lonDim, *recDim;
if (!(lvlDim = dataFile.add_dim("level", NLVL)))
return NC_ERR;
if (!(latDim = dataFile.add_dim("latitude", NLAT)))
return NC_ERR;
if (!(lonDim = dataFile.add_dim("longitude", NLON)))
return NC_ERR;
// Add an unlimited dimension...
if (!(recDim = dataFile.add_dim("time")))
return NC_ERR;
// Define the coordinate variables.
NcVar *latVar, *lonVar;
if (!(latVar = dataFile.add_var("latitude", ncFloat, latDim)))
return NC_ERR;
if (!(lonVar = dataFile.add_var("longitude", ncFloat, lonDim)))
return NC_ERR;
// Define units attributes for coordinate vars. This attaches a
// text attribute to each of the coordinate variables, containing
// the units.
if (!latVar->add_att("units", "degrees_north"))
return NC_ERR;
if (!lonVar->add_att("units", "degrees_east"))
return NC_ERR;
// Define the netCDF variables for the pressure and temperature
// data.
NcVar *presVar, *tempVar;
if (!(presVar = dataFile.add_var("pressure", ncFloat, recDim,
lvlDim, latDim, lonDim)))
return NC_ERR;
if (!(tempVar = dataFile.add_var("temperature", ncFloat, recDim,
lvlDim, latDim, lonDim)))
return NC_ERR;
// Define units attributes for data variables.
if (!presVar->add_att("units", "hPa"))
return NC_ERR;
if (!tempVar->add_att("units", "celsius"))
return NC_ERR;
// Write the coordinate variable data to the file.
if (!latVar->put(lats, NLAT))
return NC_ERR;
if (!lonVar->put(lons, NLON))
return NC_ERR;
// Write the pretend data. This will write our surface pressure and
// surface temperature data. The arrays only hold one timestep
// worth of data. We will just rewrite the same data for each
// timestep. In a real application, the data would change between
// timesteps.
for (int rec = 0; rec < NREC; rec++)
{
if (!presVar->put_rec(&pres_out[0][0][0], rec))
return NC_ERR;
if (!tempVar->put_rec(&temp_out[0][0][0], rec))
return NC_ERR;
}
// The file is automatically closed by the destructor. This frees
// up any internal netCDF resources associated with the file, and
// flushes any buffers.
cout << "*** SUCCESS writing example file pres_temp_4D.nc!" << endl;
return 0;
}
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