How to write a 3d variable to a netcdf

I want to extract a variable from an existing NetCDF file, Shift its dimensions and write the shifted variable to a new netcdf which is a copy of existing file by rewriting existing variable. So far I am able to extract a variable from an existing NetCDF file and Shift its dimensions but getting error when trying to write it to a new netcdf file

clc
clear all

data=ncread('MISR_AM1_AS_AEROSOL_P125_O075081_F13_0023.nc','/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff')
Shift= shiftdim(data,1)
copyfile(which('MISR_AM1_AS_AEROSOL_P125_O075081_F13_0023.nc'),'myfile.nc');

ncdisp('myfile.nc','/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff');
ncwrite('myfile.nc','/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff',Shift);
ncdisp('myfile.nc','/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff');

where

MISR_AM1_AS_AEROSOL_P125_O075081_F13_0023.nc

is the existing nc file

/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff

Is the subfolder and existing variable

and the error which Iam getting is

Error using netcdflib
The NetCDF library encountered an error during execution of 'putVaraDouble' function - 'Start+count exceeds dimension
bound (NC_EEDGE)'.

Error in netcdf.putVar (line 84)
netcdflib(funcstr,ncid,varid,varargin{:});

Error in internal.matlab.imagesci.nc/write (line 831)
                netcdf.putVar(gid, varid,start, count, varData);

Error in ncwrite (line 75)
ncObj.write(varName, varData, start, stride);

Error in netcdfread (line 9)
 ncwrite('myfile.nc','/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff',Shift);

Any suggetion or correction will be very much helpful,

Thanks alot in advance.

[Walter Roberson]

When you copyfile, the output file still contains all of the variables in the input file. You need to extract all of the variables and attributes and write them to the new file along with changed variable -- unless you use an external utility to delete a variable (which will end up copying etc. itself, but at least you could be sure that it would do so correctly.)

[Amalu A]

can I just create a new nc file with only one variable named '/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff' and write the shifted data to that variable?

clc
clear all

data=ncread('MISR_AM1_AS_AEROSOL_P125_O075081_F13_0023.nc','/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff')
Shift= shiftdim(data,1);
nccreate('myfile.nc','/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff1');
ncwrite('myfile.nc','/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff1',Shift);
ncdisp('myfile.nc','/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff1');

I used the above code to do so , But getting the error

Error using netcdflib
The number of input elements does not match the variable size.

Error in netcdf.putVar (line 84)
netcdflib(funcstr,ncid,varid,varargin{:});

Error in internal.matlab.imagesci.nc/write (line 803)
                netcdf.putVar(gid, varid, varData);

Error in ncwrite (line 75)
ncObj.write(varName, varData, start, stride);

Error in netcdfread (line 11)
 ncwrite('myfile.nc','/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff1',Shift);

I want to change dimension of the variable

Shift

each time because I have a number of files which have different dimensions for the variable '/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff' in a folder, Iterate through it and do the same for each of the file that is for each file in the folder I want to read, shift dimension, write to a new nc file created, So how can I specify the variable size if the newly created .nc file in advance because it is changing for each input file in the folder ?

Any suggetion will ignite a spark in my head, Thanks

[Walter Roberson]

I would have thought that what you are doing here would work -- unless, that is, that myfile.nc already exists, in which case you would be overwriting the same variable but with different size. Perhaps you should dynamically create the file name

ncvarname = '/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff');
projectdir = pwd;
dinfo = dir( fullfile(projectdir, 'MISR*AEROSOL_P125*.nc'));
filenames = fullfile(projectdir, {dinfo.name});
nfiles = length(filenames);
for K = 1 : nfiles
    filename = filenames{K};
    [folder, basename, ext] = fileparts(filename);
    newfilename = fullfile(folder, ['SASC_', basename, ext]);
    data = ncread(filename, ncvarname);
    Shift = shiftdim(data, 1);
    ncreate(newfilename, ncvarname);
    ncwrite(newfilename, ncvarname, Shift);
end

This would use the same file name as input, but prefixed with SASC_

[Amalu A]

Thanks for the reply.

I have applied your code to write that variable but I got the output file like this which is an one dimensional metrix. I have made some altrations to the code some thing like

ncvarname = '/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff'
projectdir = 'D:\inputpath\misrtry\misrcoeff';
dinfo = dir( fullfile(projectdir, 'MISR*AEROSOL_P125*.nc'));
filenames = fullfile(projectdir, {dinfo.name});
nfiles = length(filenames);
for K = 1 : nfiles
    filename = filenames{K};
    [folder, basename, ext] = fileparts(filename);
    newfilename = fullfile(folder, ['SASC_', basename, ext]);
    data = ncread(filename, ncvarname);
    Shift = shiftdim(data, 1);
    nccreate(newfilename, ncvarname,'Dimensions',{'x',size(Shift,1),'y',size(Shift,2),'z',size(Shift,3)},...
           'Format','netcdf4');
    ncwrite(newfilename, ncvarname, Shift(504,4032,3));
end

And it is saving a file with the desired dimensions, But the problem is all the values of the variable 'Spectral_AOD_Scaling_Coeff' are same somethig like 9.969209968386869e+36.

I suspect something I am doing incorrectly when writing the variable to new nc file. And here is how the output file looks like.

How can I write the values which is exacltly on the 'Shift' variable to the 'Spectral_AOD_Scaling_Coeff' variable in new nc file ?. I checked the individual array of Shift variable with squeeze function and it seems ok, But when writing to output file all values become same.

Thanks

[Amalu A]

How can I take input of 'data' variable which I want to shift from one folder and the files I want to write my 'Shift' variable from another folder through iteration, Because Iam writing my variable Shift to a nc file which is already deleted the variable '/4.4_KM_PRODUCTS/Spectral_AOD_Scaling_Coeff' and stored in another folder. I dont want to write the data to a 'newvariable' want to write to a nc file which is already in another folder Which have the same name of 'data'. When I do both things from same folder I cant Shift the data.

Thanks

[Walter Roberson]

Please experiment with the attached.

[Amalu A]

Thank you so much,