How to find the average of 3D matrices in a cell?

Question

Nilesh 2022-12-1

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评论： Walter Roberson 2022-12-2

Hello everyone,

I wish to average the 3D matrices in a cell array?

Each is a 2048 by 2048 by 100 matrix, which looks like this:

What I wish is to average each 3D matrix over the z axis (over 100), as shown below.

This will eventually lead to 1 by 3 cell, but this time, only 2048 by 2048 pixels.

The code that I have used is as follows:

for iB=1:numel(B)

meanB{iB}=mean(B{iB},3); % B is the 3D matrix

end

I have cross-cheked the values, but have found that I am not getting the right values. They are much smaller than expected.

Can anyone please help with this?

Kind regards,

Anshul

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Answer 1

Walter Roberson 2022-12-1

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https://ww2.mathworks.cn/matlabcentral/answers/1868937-how-to-find-the-average-of-3d-matrices-in-a-cell#answer_1117817

在 MATLAB Online 中打开

The code you already have should work. Or you could use the more compact

meanB = cellfun(@(b) mean(b,3), B, 'uniform', 0);

If the values are much smaller than expected, then re-check by commanding

format long g

and then examining the contents at the command line (not in the variable browser.)

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Nilesh 2022-12-2

在 MATLAB Online 中打开

Okay thank you very much.

I am still not getting the right values. Would you know if this is the correct way to create the 1 by 3 cell of 3D matrices (as shown in the first image). To do so, I have used the following:

filenum=[30, 35, 40]
B{filenum}(:,:,K)=A;%where K is length of images (100 in this case), and A reads each individual image
B=B(~cellfun('isempty',B))%Removes empty matrices

Some background imformation, there are three folders each contain 100 2D images, A is a function that reads all the images from each folder. B is the above matrix shown in the first diagram above.

I doubt this might be where the problem is coming from.