how to make 3d array by stacking 2d arrays from sentinel 5p data?

I have 36 different netcdf files for one month. Every file contains an array of 215x3245 size. Now i want to make an 3d array of size 36x215x3245 using those 36 different files. I could not upload the files as those are really big files. I can provide the code for doing this thing :

files = dir('S5P_OFFL_L2__CH4____201901*.*');

for j = 1:36
    hello(i,:,:) = ncread(files(i).name,'/PRODUCT/methane_mixing_ratio');
end

I have the file name type in the first line. Total 36 files are there with this name. Now in every file the variable '/PRODUCT/methane_mixing_ratio' has a size of 215x3245. Now I want to stack all these 36 files using loop. How can I do that? Thank you.

Answer 1

[the cyclist]

You are looping over the wrong dimension in your code. You want something like this:

files = dir('S5P_OFFL_L2__CH4____201901*.*');

% Preallocate the large array
hello = zeros(215,3245,36);

% Fill in each "slice" along the 3rd dimension
for j = 1:36
    hello(:,:,j) = ncread(files(i).name,'/PRODUCT/methane_mixing_ratio'); % Note that I shifted j to the third position
end

[SWARNENDU PAL]

Thanks for your response. I have also done the above code and for checking I have copied your code. But I got an error, which I have got previously also. the error looks like below :

Unable to perform assignment because the size of the left side is 215-by-3245 and the size of the right side is

215-by-3246.

Error in jan_2019 (line 17)

hello(:,:,j) = ncread(files(j).name,'/PRODUCT/methane_mixing_ratio'); % Note that I shifted j to the third

position

I could not understand what was the problem. I have also attached the ss of my codes. Thank you.

[the cyclist]

It means that (at least) one of your files is not 215x3245, but is actually 215x3246.

You could display the value of j during each for loop, and see what value of j you get to before the error:

for j = 1:36
    j
    hello(:,:,j) = ncread(files(i).name,'/PRODUCT/methane_mixing_ratio'); % Note that I shifted j to the third position
end

There are also more sophisticated ways to debug, using the MATLAB debugger.

[SWARNENDU PAL]

Thank you sir. You were right. The 8th file had a different dimension. One thing, can you give some way to recover from this situation?

[the cyclist]

Obviously, we cannot know why one of your input files has an extra column. That is something you'll need to figure out.

After you figure that out, it is easy to delete a single column from an array, if that is the solution:

% Define a random input
rng default
A = rand(4,3)

A = 4×3

0.8147 0.6324 0.9575 0.9058 0.0975 0.9649 0.1270 0.2785 0.1576 0.9134 0.5469 0.9706

% Delete the 2nd column:
A(:,2) = []

A = 4×2

0.8147 0.9575 0.9058 0.9649 0.1270 0.1576 0.9134 0.9706