NetCDF table

Storing tables in NetCDF4

Writting a table using Python

The following example shows how to store a table of 10 records with 8 members :

name	ADCcount	grid_i	grid_j	pressure	energy	idnumber	pressure2
16-character String	Unsigned short integer	32-bit integer	32-bit integer	float (single-precision)	double (double-precision)	Signed 64-bit integer	2-dim table of float (2*3)

The script has been run on gpc with the following modules :

module load gcc/4.8.1 hdf5/187-v18-serial-gcc netcdf/4.1.3_hdf5_serial-gcc intel/14.0.0 python/2.7.2

from netCDF4 import Dataset
from netCDF4 import chartostring, stringtoarr
import numpy

f = Dataset('particles.nc','w',format='NETCDF4')

size = 10

Particle = numpy.dtype([('name', 'S1', 16),                       # 16-character String                                                
                        ('ADCcount',numpy.uint16),                # Unsigned short integer                                             
                        ('grid_i',numpy.int32),                   # 32-bit integer                                                     
                        ('grid_j',numpy.int32),                   # 32-bit integer                                                     
                        ('pressure',numpy.float32),               # float  (single-precision)                                          
                        ('energy',numpy.float64),                 # double (double-precision)                                          
                        ('idnumber',numpy.int64),                 # Signed 64-bit integer                                              
                        ('pressure2' , numpy.float32 , (2,3) )    # array of floats (single-precision) table 2 lines * 3 columns       
                        ])

Particle_t = f.createCompoundType(Particle,'Particle')

f.createDimension('NRecords',None)
v = f.createVariable('Data',Particle_t,'NRecords')
data = numpy.empty(size,Particle)

for i in xrange(10):
    data['name'][i] = stringtoarr('Particle: %6d' % (i),16)
    data['ADCcount'][i] = (i * 256) % (1 << 16)
    data['grid_i'][i] = i
    data['grid_j'][i] = 10 - i
    data['pressure'][i] = float(i*i)
    data['energy'][i] = float(data['pressure'][i] ** 4)
    data['idnumber'][i] = i * (2 ** 34)
    data['pressure2'][i] = [
        [0.5+float(i),1.5+float(i),2.5+float(i)],
        [-1.5+float(i),-2.5+float(i),-3.5+float(i)]]
#Fill data in File                                                                                                                     
v[:] = data

f.close()