Error "Could not open file 'ncfiles'". when using a for loop to open ncfiles

2018 12 3
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更新时间：2018 12 7
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Hi
I have 469 ncfiles and I open them in a loop:
ncfiles = dir('*.nc') ;
Nfiles = length(ncfiles) ;
for i = 1:Nfiles;
ncdisp(ncfiles(i).name) ;
ncid=netcdf.open('ncfiles','NOWRITE');
varname = netcdf.inqVar(ncid);
[ndim, nvar, natt, unlim]=netcdf.inq(ncid);
end
But when I run the code I got the error when I used ncid:
Error using netcdf.open (line 52)
Could not open file 'ncfiles'.
Error in Blocking (line 9)
ncid=netcdf.open('ncfiles','NOWRITE');
I hope you can help me!

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 采纳的回答

Walter Roberson
Walter Roberson 2018-12-3

0 个投票

your file name is stored in ncfiles(i).name rather than being the literal file name 'ncfiles'

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Jonas Damsbo
Jonas Damsbo 2018-12-3
Hmm, I still got the error:
Error using netcdf.open (line 52)
Could not open file 'ncfiles(i).name'.
Error in Blocking (line 11)
ncid=netcdf.open('ncfiles(i).name','NOWRITE');
Walter Roberson
Walter Roberson 2018-12-3
not 'ncfiles(i).name' just ncfiles(i).name without the '
Jonas Damsbo
Jonas Damsbo 2018-12-3
I just try it before you have writing and it's works - thank!
Jonas Damsbo
Jonas Damsbo 2018-12-3
Hi
Maybe you can tell me how I can define my variables from my nc files?
ncfiles = dir('*.nc') ;
Nfiles = length(ncfiles) ;
for i = 1:Nfiles;
ncdisp(ncfiles(i).name) ;
ncid=netcdf.open(ncfiles(i).name,'NOWRITE');
[ndim, nvar, natt, unlim]=netcdf.inq(ncid);
end
%Defines longitudes, latitudes, time and z
lon = ncread(ncfiles(i).name,'longitude') ; nx = length(lon) ;
lat = ncread(ncfiles(i).name,'latitude') ; ny = length(lat) ;
time = ncread(ncfiles(i).name,'time') ; nt = length(time);
z = ncread(ncfiles(i).name,'z') ; nz = length(z);
Right now I get my different variables:
lat = 181 x 1 (181 values of size 9.9692e + 36)
lon = 360 x 1 (181 values of size 9.9692e + 36)
time = []
z = []
Walter Roberson
Walter Roberson 2018-12-3
Every iteration you are overwriting ndim and so on . You are also not closing ncid .
The information about variables including their names can be extracted using ncinfo() instead of going into netcdf.* .
You can use dynamic field names to store variables:
loaded_file{i}.(these_variable_names{K})) = ncread(FILENAME, these_variable_names{K});
If you can count on the files all having the same variable names then use (i) instead of {i}
Jonas Damsbo
Jonas Damsbo 2018-12-5
Okay so I try this:
ncfiles = dir('*.nc') ;
Nfiles = length(ncfiles) ;
for i = 1:Nfiles;
ncdisp(ncfiles(i).name) ;
ncid=netcdf.open(ncfiles(i).name,'NOWRITE');
%[ndim, nvar, natt, unlim]=netcdf.inq(ncid);
netcdf.close(ncid);
end
ncvars = {'longitude','latitude','time','z'};
for i = 1:Nfiles
lon(i) = ncread(ncfiles(i).name, ncvars{1}); nx = length(lon(i));
lat(i) = ncread(ncfiles(i).name, ncvars{2}); ny = length(lat(i));
time(i) = ncread(ncfiles(i).name, ncvars{3}); nt = length(time(i));
z(i) = ncread(ncfiles(i).name, ncvars{4}); nz = length(z(i));
end
But now I get the error "Unable to perform assignment because the indices on the left side are not compatible with the size of the right side".
My files have the same variables. The left side and the right side - it is thes sizes in ncread?
Walter Roberson
Walter Roberson 2018-12-5
编辑：Walter Roberson 2018-12-5
The result of ncread() is the complete content of the variable you indicate to read. That will not generally be a scalar, but you are assigning it to a scalar location.
You should consider using cell arrays. And watch out because length() is the max() of the dimensions, not any one particular dimension.
Jonas Damsbo
Jonas Damsbo 2018-12-7
Such like that?
%Indlæser alle filer fra folderen
ncfiles = dir('*.nc') ;
Nfiles = length(ncfiles) ;
for i = 1:Nfiles;
ncdisp(ncfiles(i).name) ;
ncid=netcdf.open(ncfiles(i).name,'NOWRITE');
%[ndim, nvar, natt, unlim]=netcdf.inq(ncid);
netcdf.close(ncid);
end
lat = cell(Nfiles, 1);
lon = cell(Nfiles, 1);
time = cell(Nfiles, 1);
z = cell(Nfiles, 1);
for i = 1:Nfiles
lon(i) = ncread(ncfiles(i).name, 'longitude'); %nx = length(lon(i));
lat(i) = ncread(ncfiles(i).name, 'latitude'); %ny = length(lat(i));
time(i) = ncread(ncfiles(i).name, 'time'); %nt = length(time(i));
z(i) = ncread(ncfiles(i).name, 'z'); %nz = length(z(i));
end
Because now I get the error "Conversion to cell from single is not possible."

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