Writing a NetCDF file with Matlab and R

Language

MATLAB

file_name = 'test.nc';
var1_name = 'tmp1';
file2_name = 'test2.nc';
var2_name = 'tmp2';
 
 
% Create a netcdf 4 file with a variable
nccreate(file_name, 'myvariable');
% A netcdf 4 file with a variable and its attributes
nccreate(file2_name, var2_name,'Dimensions', {'r' 12 'c' 14 }, 'Datatype' , 'single')
 
 
% Write data to the netcdf file
nccreate(file2_name,'var');
ncwrite(file2_name,'var',4.5);
% Modify the data
ncwrite(file2_name,'var',8.3);
% Add an attribute
ncwriteatt(file2_name, var2_name, 'tmp', 'ok');
 
 
% Write data from an existing netcdf file to another
data_source = ncread(file2_name, 'var');
nccreate(file_name,'var');
ncwrite(file_name, 'var', data_source);
 
 
% Modify the structure of the netcdf file
file_info = ncinfo(file_name,'/')
file_schema.Name = '/';
file_schema.Format = 'netcdf4_classic';
file_schema.Dimensions(1).Name   = 'first';
file_schema.Dimensions(1).Length = 2;
file_schema.Dimensions(2).Name   = 'second';
file_schema.Dimensions(2).Length = 30;
file_schema.Dimensions(3).Name   = 'third';
file_schema.Dimensions(3).Length = 1;
ncwriteschema(file_name, file_schema);
 
 
%  Modify the structure of the variable 'new_var'
var_info =  ncinfo(file_name,'myvariable')
var_schema.Name   = 'new_var';
var_schema.Dimensions(1).Name   = 'thefirst';
var_schema.Dimensions(1).Length = 2;
var_schema.Datatype = 'double';
ncwriteschema(file_name, var_schema);

R

#Intall the NetCDF libraries: sudo apt-get install libnetcdf-dev 
#Install the ncdf package in R: install.packages("ncdf")
 
library("ncdf")
 
# Define netcdf dimensions: name, units and value
dim1 <- dim.def.ncdf("x", "m", seq(1, 200, 40))
dim2 <- dim.def.ncdf("y", "A", 10)
dim3 <- dim.def.ncdf("z", "L", 19)
 
# Define objets of class var.def.ncdf for the netcdf file with its name, units, dimension(s) and missing value
var1 <- var.def.ncdf("my_var1", "degrees", dim1, -999)
var2 <- var.def.ncdf("my_var2", "degrees", dim1, -999, longname = "things", prec = "integer")
var3 <- var.def.ncdf("my_var3", "degrees", list(dim1, dim2), -999, longname = "An example of 2-dim variable")
 
# Create a netcdf file with its variables var1, var2 and var3
filename <- "/home/ndiaye/Projets/R/test.nc"
fid <- create.ncdf(filename, list(var1, var2))
 
# Close the file for having it written to disk
close.ncdf(fid)
 
# Add a variable to the netcdf file
fid <- open.ncdf(filename, write=TRUE)
var.add.ncdf(fid, var3)
 
# Write data to a netcdf file
data1 <- c(1,2,3,4,5,6)
put.var.ncdf(fid, var1, data1)
data2 <- matrix(c(128, 2, 1, 0, 8, 9, 180, 31, 8, 24, 5, 7, 81, 62, 541, 0, 54, 36, 0, 54, 36), ncol = 4)
put.var.ncdf(fid, var3, data2, start = c(2,1), count = c(3,1) )
 
# Close netcdf file access
close.ncdf(fid)

More news

Highlights

AERIS/ICARE was migrated his good old FTP server to SFTP

For security reason, we are abandoning the FTP protocol in favor of SFTP on our distribution server. Depending of the way you are using this service, you can have to change the commands you are used to. Note that not all applications support the SFTP protocol, and some additional tools may need to be installed […]

01.03.2024

Tutorials

How to convert a matplotlib figure to a numpy array or a PIL image

Language/Format: Python
Description: For manipulating a figure build with matplotlib, it is sometimes requested to convert it in a format understandable by other python libraries. This can be useful for using scipy image filters or manually adding annotations for example.
This page details how to convert a matplotlib figure to a numpy 3D array of RGBA values, or directly to a PIL ( Python Imaging Library ) Image.
Author(s): Nicolas Pascal (ICARE)

10.02.2017

Tutorials

Reading a NetCDF file with Matlab and R

Language/Format: MATLAB
Description: This page gives pieces of code to read data in a NetCDF file
Author(s): Aminata NDIAYE (ICARE)

15.12.2015

Search