int main()
{
// This is the data array we will write. It will just be filled
// with a progression of numbers for this example.
int dataOut[NX][NY];
// 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 i = 0; i < NX; i++)
for(int j = 0; j < NY; j++)
dataOut[i][j] = i * NY + j;
// The default behavior of the C++ API is to throw an exception i
// an error occurs. A try catch block is necessary.
try
{
// Create the file. The Replace parameter tells netCDF to overwrite
// this file, if it already exists.
NcFile dataFile("simple_xy.nc", NcFile::replace);
// Create netCDF dimensions
NcDim xDim = dataFile.addDim("x", NX);
NcDim yDim = dataFile.addDim("y", NY);
// Define the variable. The type of the variable in this case is
// ncInt (32-bit integer).
vector<NcDim> dims;
dims.push_back(xDim);
dims.push_back(yDim);
NcVar data = dataFile.addVar("data", ncInt, dims);
// Write the data to the file. Although netCDF supports
// reading and writing subsets of data, in this case we write all
// the data in one operation.
data.putVar(dataOut);
// The file will be automatically close when the NcFile object goes
// out of scope. This frees up any internal netCDF resources
// associated with the file, and flushes any buffers.
//cout << "*** SUCCESS writing example file simple_xy.nc!" << endl;
return 0;
}
catch(NcException& e)
{e.what();
return NC_ERR;
}
}
int main()
{
// We will write latitude and longitude fields.
float lats[NLAT],lons[NLON];
// Program variables to 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; //used in the data generation loop
// 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] =(float) (SAMPLE_PRESSURE + i);
temp_out[lvl][lat][lon] = (float)(SAMPLE_TEMP + i++);
}
try
{
// Create the file.
NcFile test(FILE_NAME, NcFile::replace);
// Define the dimensions. NetCDF will hand back an ncDim object for
// each.
NcDim lvlDim = test.addDim(LVL_NAME, NLVL);
NcDim latDim = test.addDim(LAT_NAME, NLAT);
NcDim lonDim = test.addDim(LON_NAME, NLON);
NcDim recDim = test.addDim(REC_NAME); //adds an unlimited dimension
// Define the coordinate variables.
NcVar latVar = test.addVar(LAT_NAME, ncFloat, latDim);
NcVar lonVar = test.addVar(LON_NAME, ncFloat, lonDim);
// Define units attributes for coordinate vars. This attaches a
// text attribute to each of the coordinate variables, containing
// the units.
latVar.putAtt(UNITS, DEGREES_NORTH);
lonVar.putAtt(UNITS, DEGREES_EAST);
// Define the netCDF variables for the pressure and temperature
// data.
vector<NcDim> dimVector;
dimVector.push_back(recDim);
dimVector.push_back(lvlDim);
dimVector.push_back(latDim);
dimVector.push_back(lonDim);
NcVar pressVar = test.addVar(PRES_NAME, ncFloat, dimVector);
NcVar tempVar = test.addVar(TEMP_NAME, ncFloat, dimVector);
// Define units attributes for coordinate vars. This attaches a
// text attribute to each of the coordinate variables, containing
// the units.
pressVar.putAtt(UNITS, PRES_UNITS);
tempVar.putAtt(UNITS, TEMP_UNITS);
// Write the coordinate variable data to the file.
latVar.putVar(lats);
lonVar.putVar(lons);
// 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.
vector<size_t> startp,countp;
startp.push_back(0);
startp.push_back(0);
startp.push_back(0);
startp.push_back(0);
countp.push_back(1);
countp.push_back(NLVL);
countp.push_back(NLAT);
countp.push_back(NLON);
for (size_t rec = 0; rec < NREC; rec++)
{
startp[0]=rec;
pressVar.putVar(startp,countp,pres_out);
tempVar.putVar(startp,countp,temp_out);
}
// 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 " << FILE_NAME << "!" << endl;
return 0;
}
catch(NcException& e)
{
e.what();
return NC_ERR;
}
}
int main(void)
{
// We will write surface temperature and pressure fields.
float presOut[NLAT][NLON];
float tempOut[NLAT][NLON];
float lats[NLAT];
float lons[NLON];
// In addition to the latitude and longitude dimensions, we will
// also create latitude and longitude netCDF variables which will
// hold the actual latitudes and longitudes. Since they hold data
// about the coordinate system, the netCDF term for these is:
// "coordinate variables."
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;
// 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++)
for(int lon = 0; lon < NLON; lon++)
{
presOut[lat][lon] = SAMPLE_PRESSURE + (lon * NLAT + lat);
tempOut[lat][lon] = SAMPLE_TEMP + .25 * (lon * NLAT +lat);
}
try
{
// Create the file. The Replace parameter tells netCDF to overwrite
// this file, if it already exists.
NcFile sfc(FILE_NAME, NcFile::replace);
// Define the dimensions. NetCDF will hand back an ncDim object for
// each.
NcDim latDim = sfc.addDim(LAT_NAME, NLAT);
NcDim lonDim = sfc.addDim(LON_NAME, NLON);
// Define coordinate netCDF variables. They will hold the
// coordinate information, that is, the latitudes and
// longitudes. An pointer to a NcVar object is returned for
// each.
NcVar latVar = sfc.addVar(LAT_NAME, ncFloat, latDim);//creates variable
NcVar lonVar = sfc.addVar(LON_NAME, ncFloat, lonDim);
// Write the coordinate variable data. This will put the latitudes
// and longitudes of our data grid into the netCDF file.
latVar.putVar(lats);
lonVar.putVar(lons);
// Define units attributes for coordinate vars. This attaches a
// text attribute to each of the coordinate variables, containing
// the units. Note that we are not writing a trailing NULL, just
// "units", because the reading program may be fortran which does
// not use null-terminated strings. In general it is up to the
// reading C program to ensure that it puts null-terminators on
// strings where necessary.
lonVar.putAtt(UNITS,DEGREES_EAST);
latVar.putAtt(UNITS,DEGREES_NORTH);
// Define the netCDF data variables.
vector<NcDim> dims;
dims.push_back(latDim);
dims.push_back(lonDim);
NcVar presVar = sfc.addVar(PRES_NAME, ncFloat, dims);
NcVar tempVar = sfc.addVar(TEMP_NAME, ncFloat, dims);
// Define units attributes for vars.
presVar.putAtt(UNITS,"hPa");
tempVar.putAtt(UNITS,"celsius");
// Write the pretend data. This will write our surface pressure and
// surface temperature data. The arrays of data are the same size
// as the netCDF variables we have defined.
presVar.putVar(presOut);
tempVar.putVar(tempOut);
// 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 " << FILE_NAME << "!" << endl;
return 0;
}
catch(NcException& e)
{
e.what();
return NC_ERR;
}
}
