MATLAB Answers

Converting a 3D Matrix to multiple 2D matrices

34 views (last 30 days)
Aldo Hernandez
Aldo Hernandez on 17 Jan 2021
Edited: Bruno Luong on 17 Jan 2021
I have a 3D matrix, 1000 x 1000 x 40
I want to convert this matrix to 40 different matrices, 1000 x 1000 each. I suppose I am asking for the inverse of repmat, however searches into that have not led to progress.
Any help is appreciated.

  2 Comments

Athrey Ranjith Krishnanunni
Something like this?
largeMatrix = randn(1000,1000,40);
smallMatrixArray = cell(40,1);
for iOuterDim = 1:40
smallMatrixArray{iOuterDim} = largeMatrix(:,:,iOuterDim);
end
Steven Lord
Steven Lord on 17 Jan 2021
I want to convert this matrix to 40 different matrices
Why? What benefit do you hope to gain by doing that instead of indexing into the array to retrieve the appropriate slice when needed?
A = reshape(1:(3*4*5), [3 4 5]);
A4 = A(:, :, 4)
A4 = 3×4
37 40 43 46 38 41 44 47 39 42 45 48
What happens when or if you expand your problem sizes to an array of size 10000 in the third dimension? Your workspace would become awfully cluttered with ten thousand and one arrays in it.

Sign in to comment.

Accepted Answer

Bruno Luong
Bruno Luong on 17 Jan 2021
Edited: Bruno Luong on 17 Jan 2021
Assuming A is array 1000 x 1000 x 40
C = num2cell(A,[1 2]);

  2 Comments

Athrey Ranjith Krishnanunni
You'll have to write
C = shiftdim(num2cell(A,[1 2]));
to get rid of the leading singleton dimensions, though.
Bruno Luong
Bruno Luong on 17 Jan 2021
Well it is nicer but it is not requirement by OP.
C{k} still give the the kth matrix as requested.

Sign in to comment.

More Answers (0)

Products


Release

R2019b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!