Export 2 Dimension out of a 3 dimensionoal Array

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Mouse 2021-11-8

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https://ww2.mathworks.cn/matlabcentral/answers/1581694-export-2-dimension-out-of-a-3-dimensionoal-array

评论： Star Strider 2021-11-8

Hi

I hava a 3D Array. Now I like to save the content of the 3d array in n 2d arrays

2dArray = zeros(size(3dArray([1],:,:)));
for z = 1: size(3dArray(:)
    2dArray(z)=3dArray(z,:,:)
end

What am I doing wrong?

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Answer 1

Star Strider 2021-11-8

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https://ww2.mathworks.cn/matlabcentral/answers/1581694-export-2-dimension-out-of-a-3-dimensionoal-array#answer_826564

在 MATLAB Online 中打开

I am not certain what is the desired result.

Usually, the intent is to separate the ‘pages’ (third dimension) of the array into separate 2D arrays.

Likely the best option for that is —

Array3D = randi(9, 3, 4, 4);
Array3D(:,:,2)                                          % Display Page (Dleete Later)
ans = 3×4
     2     8     7     2
     8     2     6     4
     1     9     3     6
A3dsz = size(Array3D)
A3dsz = 1×3
     3     4     4
Arrays2D = mat2cell(Array3D, A3dsz(1), A3dsz(2), ones(1,A3dsz(3)));
Arrays2D{2}                                             % Display Result
ans = 3×4
     2     8     7     2
     8     2     6     4
     1     9     3     6

Make appropriate changes to get the desired result.

.

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Star Strider 2021-11-8

在 MATLAB Online 中打开

I am not certain what the desired result is.

My initial response demonstrated how to save it in 3 different cell arrays, so to do that, the code changes to —

Array3D = randi(9, 3, 5, 4);
Array3D(2,:,:)                                          % Display Page (Delete Later)
ans = 
ans(:,:,1) =

     9     7     9     5     1


ans(:,:,2) =

     8     1     8     4     9


ans(:,:,3) =

     8     5     1     2     3


ans(:,:,4) =

     4     9     6     3     8
squeeze(Array3D(2,:,:))                                 % Display Page (Delete Later)
ans = 5×4
     9     8     8     4
     7     1     5     9
     9     8     1     6
     5     4     2     3
     1     9     3     8
A3dsz = size(Array3D)
A3dsz = 1×3
     3     5     4
Arrays2D = mat2cell(Array3D, ones(1,A3dsz(1)), A3dsz(2), A3dsz(3));
Arrays2D{2}                                             % Display Result
ans = 
ans(:,:,1) =

     9     7     9     5     1


ans(:,:,2) =

     8     1     8     4     9


ans(:,:,3) =

     8     5     1     2     3


ans(:,:,4) =

     4     9     6     3     8
squeeze(Arrays2D{2})                                      % Display Result
ans = 5×4
     9     8     8     4
     7     1     5     9
     9     8     1     6
     5     4     2     3
     1     9     3     8

Make appropriate changes to get different results.

I do not recommend using reshape to save it to a single 2D matrix, because that creates significant indexing complications.

.

Mouse 2021-11-8

在 MATLAB Online 中打开

data3D=rand(3,3883,280);        %create a 3D array
for i = 1: 3                    %now separate every page of the 3D array into 2D arrays
    oneDataSet = data3D(i,:,:); %cut away a page "slide"
    data_2D=squeeze(oneDataSet);%put away the information that this is a page. Only Information about 2D Array will stay
end

this is my solution to convert a 3 Dimensional Array

Star Strider 2021-11-8

在 MATLAB Online 中打开

The code in Comment overwrites ‘data_2D’ in every loop iteration. Only one (the last) 2D matrix created will result.

My code produces 3 separate matrices as cell arrays.

A small addition to it will squeeze all of them as well —

Array3D = randi(9, 3, 5, 4);
Array3D(2,:,:);                                         % Display Page (Delete Later)
squeeze(Array3D(2,:,:))                                 % Display Page (Delete Later)
ans = 5×4
     6     9     2     9
     7     8     5     8
     8     1     8     7
     5     7     1     8
     6     1     7     6
A3dsz = size(Array3D);
Arrays2D = mat2cell(Array3D, ones(1,A3dsz(1)), A3dsz(2), A3dsz(3));
Arrays2D{2};                                            % Display Result
Arrays2D = cellfun(@squeeze, Arrays2D, 'Unif',0);       % Display Result
Arrays2D{2}
ans = 5×4
     6     9     2     9
     7     8     5     8
     8     1     8     7
     5     7     1     8
     6     1     7     6