MATLAB：将“ vertcat”反转（将2D转换为3D）

Question

I'm looking for an efficient way to split a huge 2D matrix into several blocks and transfer these blocks into the 3rd dimension.

Take mat_orig ( 100x10 ). After every other 20 rows, I need to make a cut and put the resulting block into the 3rd dimension. That is, my 100x10 matrix must result in a 20x10x5 matrix.

My solution involves mat2cell, permute, and cell2mat. It's working, however, I'm working on quite some large matrices. I am wondering if somebody feels challenged and can provide a more sophisticated (faster) solution?

mat_orig = reshape(1:1000, 10, 100)';
mat_len = 20;
num_pages = size(mat_orig, 1) / mat_len;

tic;
mat_splitted = cell2mat(permute(mat2cell(mat_orig, ones(1, num_pages) * 
size(mat_orig, 1) / num_pages, 10), [3, 2,1]));
toc (% Elapsed time is 0.108561 seconds.)



mat_orig = reshape(1:100000000, 10, 10000000)';
mat_len = 10000;
num_pages = size(mat_orig, 1) / mat_len;

tic;
mat_splitted = cell2mat(permute(mat2cell(mat_orig, ones(1, num_pages) * 
size(mat_orig, 1) / num_pages, 10), [3, 2,1]));
toc (% Elapsed time is 4.361126 seconds.)

Answer 1

You can avoid cell2mat :

N = 20; % number of rows per block
mat_split = permute(reshape(mat_orig, N, [], size(mat_orig,2)), [1 3 2]);