change variable data type from a NetCDF file

21 views (last 30 days)
flashpode
flashpode on 18 Oct 2021
Edited: Rupesh on 29 Feb 2024
I've got a NetCDF file that has many different variables that are int16, int32 and single and I want to convert them to chars or strings.
How could I do it.

Answers (1)

Rupesh
Rupesh on 22 Feb 2024
Edited: Rupesh on 29 Feb 2024
Hi flashpode,
I understand that you have a NetCDF file containing a range of variables with different data types, specifically variables stored as int16, int32, and single (floating-point). You want to convert the values of these variables from their original numeric data types into characters or strings.
To achieve this, you can follow the below steps.
  • Open the “NetCDF” file using MATLAB functions designed to interact with such files.
  • Identify the variables you wish to convert by obtaining their variable IDs.
  • Read the data from these variables into MATLAB's workspace.
  • Convert the numeric data into strings. This could be done elementwise for vectors or cell-by-cell for matrices. MATLAB provides several functions for this purpose, such as “num2str”, “int2str”, or the string functions, depending on whether you want to create character arrays or string arrays.
  • Ensure the conversion maintains the original data's precision and format, so the numerical values are accurately represented as strings.
  • Close the “NetCDF” file once the operations are complete.
This process would transform the numeric data into a format suitable for text-based processing or display, while preserving the original values as accurately as possible in string form.
Below 2 scripts will give you a code overview of how you can create and save as well as modify the variable in any conversion type you want.
% Name of the sample NetCDF file
filename = 'sample.nc';
% Create the NetCDF file
ncid = netcdf.create(filename, 'CLOBBER');
% Define dimensions
dimid_x = netcdf.defDim(ncid, 'x', 10); % Dimension of length 10
% Define variables with different data types
varid_int16 = netcdf.defVar(ncid, 'var_int16', 'short', dimid_x);
varid_int32 = netcdf.defVar(ncid, 'var_int32', 'int', dimid_x);
varid_single = netcdf.defVar(ncid, 'var_single', 'float', dimid_x);
% End definitions and enter data mode
netcdf.endDef(ncid);
% Create sample data for each variable
data_int16 = int16(1:10);
data_int32 = int32(11:20);
data_single = single(21:30);
% Write sample data to the file
netcdf.putVar(ncid, varid_int16, data_int16);
netcdf.putVar(ncid, varid_int32, data_int32);
netcdf.putVar(ncid, varid_single, data_single);
% Close the NetCDF file
netcdf.close(ncid);
In above script variables are created and are stored for their type conversions to string in part 2.
% Re-open the NetCDF file for reading
ncid = netcdf.open(filename, 'NC_NOWRITE');
% Get variable IDs for the variables we created earlier
varid_int16 = netcdf.inqVarID(ncid, 'var_int16');
varid_int32 = netcdf.inqVarID(ncid, 'var_int32');
varid_single = netcdf.inqVarID(ncid, 'var_single');
% Read the data from the file
data_int16 = netcdf.getVar(ncid, varid_int16);
data_int32 = netcdf.getVar(ncid, varid_int32);
data_single = netcdf.getVar(ncid, varid_single);
% Convert the data to strings
str_int16 = string(data_int16);
str_int32 = string(data_int32);
str_single = string(data_single);
% Close the NetCDF file
netcdf.close(ncid);
disp(['String representation of int16 data: ' strjoin(str_int16, ', ')]);
disp(['String representation of int32 data: ' strjoin(str_int32, ', ')]);
disp(['String representation of single data: ' strjoin(str_single, ', ')]);
Here is the expected output.
"String representation of int16 data: "1, 2, 3, 4, 5, 6, 7, 8, 9, 10"
"String representation of int32 data: "11, 12, 13, 14, 15, 16, 17, 18, 19, 20"
"String representation of single data: "21, 22, 23, 24, 25, 26, 27, 28, 29, 30"
You can refer to following documents for more information regarding about how one can read data from variable in netCDF data source.
Hope this helps!

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!