All values I am trying to extract from my NetCDF file results in NaN values

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Leeza Pickering 2022-7-21

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回答： Aditya 2023-10-6

Hello!

I am new to using matlab and I am attempting to extract values from an ERA-5 Land NetCDF file. I sucessfully managed to do this online but now I have decided to use the latest downloaded version of Matlab and all my results are NaN values. Please may anyone advise me with how to sucessfully run this on my desktop?

The last two results from my command line:

AirTemp1(:,:,8760) =

NaN

Final_Table =

0×0 empty cell array

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MJFcoNaN 2022-7-22

Hello，

Please post more codes about reading and dealing with your nc files. The result of ncdisp and ncinfo will help too.

KSSV 2022-7-22

Show us your nc file and the code. REading nd fil ein MATLAB should be very easy.

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Answer 1

Aditya 2023-10-6

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Hi Leeza,

From your query, I understand that you are facing an issue reading a NetCDF file in MATLAB. To assess this issue I have created a sample test file, and it appears to be working correctly.

Please find the code snippet below, which demonstrates the creation of a sample NetCDF file with random values and the subsequent reading of the data:

% Create sample data 
lat = -90:10:90; 
lon = -180:20:180; 
time = datetime('2022-01-01'):hours(1):datetime('2022-01-02'); 
time_numeric = datenum(time); % Convert datetime to double 
data = randn(length(lat), length(lon), length(time)); 
% Create NetCDF file 
ncfile = 'sample_data.nc'; 
nccreate(ncfile, 'lat', 'Dimensions', {'lat', length(lat)}); 
nccreate(ncfile, 'lon', 'Dimensions', {'lon', length(lon)}); 
nccreate(ncfile, 'time', 'Dimensions', {'time', length(time)}); 
nccreate(ncfile, 'data', 'Dimensions', {'lat', length(lat), 'lon', length(lon), 'time', length(time)}); 
% Write data to NetCDF file 
ncwrite(ncfile, 'lat', lat); 
ncwrite(ncfile, 'lon', lon); 
ncwrite(ncfile, 'time', time_numeric); % Use converted double data 
ncwrite(ncfile, 'data', data); 
% Read the latitude, longitude, time, and data variables 
lat1 = ncread(ncfile, 'lat'); 
lon1 = ncread(ncfile, 'lon'); 
time1 = ncread(ncfile, 'time'); 
data1 = ncread(ncfile, 'data'); 
% Specify the indices for the desired data point 
lat_index = 3;   % Example: 3rd latitude index 
lon_index = 5;   % Example: 5th longitude index 
time_index = 10; % Example: 10th time index 
disp(size(data1)) 
% Access the data at the specified indices 
value = data1(:,:, time_index); 
% Display the value 
disp(value); 