reshape 4-dimension array

I have an array dimensioned A(m,m,M,M). I would like to "reshape" this so that each mxm block is in the correct position in a B(m*M,m*M) matrix where the correct position is indicated by the third and fourth indices.

Can someone show me a straightforward way to do this?

Answer 1

[Stephen23]

https://www.mathworks.com/help/matlab/ref/double.permute.html

https://www.mathworks.com/help/matlab/ref/double.reshape.html

A = randi(9,3,3,5,5);
[~,M,~,N] = size(A);
B = permute(A,[1,3,2,4]);
B = reshape(B,[M*N,M*N])

B = 15×15

3 1 4 2 7 7 4 7 8 5 7 2 4 7 7 1 9 1 2 2 5 9 8 2 5 6 1 7 8 3 7 6 2 3 4 3 6 8 9 5 7 5 2 7 6 4 1 9 6 4 3 2 9 1 9 4 8 7 1 6 1 2 7 3 1 8 9 9 4 2 5 7 2 9 5 8 5 8 8 3 5 8 6 4 1 4 3 8 3 9 2 6 7 3 2 2 5 7 9 4 2 2 5 9 3 9 4 4 2 7 3 8 8 9 7 3 2 9 8 7 7 2 3 2 9 7 2 4 6 7 7 9 3 6 8 5 5 4 1 9 5 4 1 5 2 1 4 3 8 5

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Checking some random block:

X = 3;
Y = 5;
A(:,:,X,Y)

ans = 3×3

5 9 3 9 8 7 3 6 8

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B(...
    ((X-1)*M+1):(X*M),...
    ((Y-1)*M+1):(Y*M))

ans = 3×3

5 9 3 9 8 7 3 6 8

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[Bill Greene]

Fantasitic, thanks!

Answer 2

[Matt J]

Download this File Exchange package,

https://www.mathworks.com/matlabcentral/fileexchange/115340-block-transposition-permutation-and-reshaping-of-arrays?s_tid=blogs_rc_6

and do the whole thing in one line,

B=blkReshape(A,[m,m],[M,M]);