Creating netcdf file error

I am trying to create a .nc file and with the following script as my example:

% Intialise file

nc=netcdf('my_file.nc','clobber');

% Define DIMS

ncdim('LATS',length(Y),nc);

ncdim('LONS',length(X),nc);

ncvar('LATS','double',{'LATS'},nc);

nc{'LATS'}(:) = Y';

Doing this i get the error:

??? Error: File: /home/matlab/toolbox/netcdf/@ncvar/subsasgn.m Line: 118 Column: 9 "subs" previously appeared to be used as a function or command, conflicting with its use here as the name of a variable. A possible cause of this error is that you forgot to initialize the variable, or you have initialized it implicitly using load or eval.

Error in ==> netcdf.subsasgn at 83 result = subsasgn(v, s, other);

Any help?? I cannot seem to assign values to variable that I am trying to create.

Answer 1

[Dave Correa]

Hello;

I'm leaving you an example.

I hope this is of some help.

Regards

Dave Correa

E-mail:[e-mail]

http://fismatlab.blogspot.com/

close all, clear all, clc

yearini=1960;
yearfin=1970;
%%--------------------
nt=144;
nx=1440;
ny=720;

lon=linspace(-180,180,nx);
lat=linspace(90,-90,ny);
time=1:nt;
[mlat,mlon]=meshgrid(lat,lon);

disp('Creando file Netcdf...')
filenc=['Data.nc'];
ncid = netcdf.create(filenc,'NC_WRITE');
% Crear dimensiones
dimid_lon = netcdf.defDim(ncid,'longitude',nx);
dimid_lat = netcdf.defDim(ncid,'latitude',ny); 
dimid_time = netcdf.defDim(ncid,'time',nt); 
% Crear variables y atributos
varid_lon = netcdf.defVar(ncid,'longitude','double',dimid_lon);
netcdf.putAtt(ncid,varid_lon,'long_name','Longitude')
netcdf.putAtt(ncid,varid_lon,'units','degrees_east')
% 
varid_lat = netcdf.defVar(ncid,'latitude','double',dimid_lat);
netcdf.putAtt(ncid,varid_lat,'long_name','Latitude')
netcdf.putAtt(ncid,varid_lat,'units','degrees_north')
%
varid_time = netcdf.defVar(ncid,'time','double',dimid_time);
netcdf.putAtt(ncid,varid_time,'long_name','Time')
netcdf.putAtt(ncid,varid_time,'units','Months since 1960-01-01 00:00:00')
% 
varid_prec = netcdf.defVar(ncid,'prec','double',[dimid_lon,dimid_lat,dimid_time]);
netcdf.putAtt(ncid,varid_prec,'long_name','Variable')
netcdf.putAtt(ncid,varid_prec,'units','mm')
netcdf.putAtt(ncid,varid_prec,'missing_value',-9999)
netcdf.endDef(ncid)
% % % Agregar datos de coordenadas
netcdf.putVar(ncid,varid_lon,lon);
netcdf.putVar(ncid,varid_lat,lat);
netcdf.putVar(ncid,varid_time,time);

m=1;
for year=yearini:yearfin   
for mes=1:12    

netcdf.putVar(ncid,varid_prec,[0 0 m-1],[nx ny 1],tmp);

m=m+1;
end
end
netcdf.close(ncid)

[Evan]

Hi Dave,

Thanks very much for the reply. One more question is whether or not you can assign cell or char array to a nc variable.

For example, I currently have a cell array of size 25 x 1 named titles consisting of 25 titles that I want to save in the netcdf file. If I convert this to char the dims now are 25 x 14.

I was trying to assign the variable as such:

ncdim('TITLES',length(titles),ncfile); % length(titles) is 25

nc{'TITLES'}=ncchar('TITLES'); nc{'TITLES'}(:)=titles;

But received this message:

## Conversion to double from cell is not possible.

So I tried:

nc{'TITLES'}(:)=char(titles);

But received this message:

??? In an assignment A(:) = B, the number of elements in A and B must be the same.

This is I assume because the dims are now 25 x 14?

How do I assign cell or char arrays to a netcdf variable

[Walter Roberson]

You are unlikely to be able to use a string as a cell array subscript. Notice that Dave never uses any syntax like that.

[Ashish Uthama]

Evan, I believe you are using a 3rd party toolbox. Dave's answer uses MATLAB's internal netcdf package. It does not support {} indexing (its a thin wrapper around the netcdf library from Unidata).

Answer 2

[Dave Correa]

Dear Evan;

I'm using the native NetCDF toolbox Matlab. For your question, Yes, you can use text in a cell to create variable names. I leave you an example.

I hope this is of some help.

regards

Dave Correa

E-mail:[e-mail]

http://fismatlab.blogspot.com/

Example:

clc,close all,clear all

% Create file NetCDF.
nx=320;     % Length of Longitud 
ny=639;     % Length of Latitude 
nt=12;      % Length of Time

disp('Create file Netcdf...')
filenc=['example_nc.nc'];

ncid = netcdf.create(filenc,'NC_WRITE');

% Create dimensions
dimid_lon = netcdf.defDim(ncid,'longitude',nx);
dimid_lat = netcdf.defDim(ncid,'latitude',ny); 
dimid_time = netcdf.defDim(ncid,'time',nt); 

%  Create variables y atributtes of referencia Spacial and time
varid_lon = netcdf.defVar(ncid,'longitude','double',dimid_lon);
netcdf.putAtt(ncid,varid_lon,'long_name','Longitude')
netcdf.putAtt(ncid,varid_lon,'units','degrees_east')

varid_lat = netcdf.defVar(ncid,'latitude','double',dimid_lat);
netcdf.putAtt(ncid,varid_lat,'long_name','Latitude')
netcdf.putAtt(ncid,varid_lat,'units','degrees_north')

varid_time = netcdf.defVar(ncid,'time','double',dimid_time);
netcdf.putAtt(ncid,varid_time,'long_name','Time')
netcdf.putAtt(ncid,varid_time,'units','Days since 1981-09-27 00:00:00')

% Define cell with variable name
variable={'var_01','var_02','var_03','var_04','var_05','var_06','var_07',...
    'var_08','var_09','var_10','var_11','var_12','var_13','var_14','var_15'};

for n=1:length(variable)
vari=variable{n};       % Save name temporal of n variable

% Create variable n
varid_var = netcdf.defVar(ncid,vari,'double',[dimid_lon,dimid_lat,dimid_time]);
netcdf.putAtt(ncid,varid_var,'long_name',vari)
netcdf.putAtt(ncid,varid_var,'units','[Unit]')
netcdf.putAtt(ncid,varid_var,'missing_value',-9999)

% Assign values to variables
% In this section we assign values to each of the variables
% 
end

netcdf.endDef(ncid)     % Finaly definition of variables
netcdf.close(ncid)      % Close file NetCDF.

% Verificate NetCDF file create
ncid = netcdf.open('example_nc.nc','NOWRITE');
[ndims,nvars,ngatts,unlimdimid] = netcdf.inq(ncid);

nvars