MATLAB: Saving the output matrices of for loop

for loopmatrices

if i have (for loop) (for i=1:r) which generate a matrix of (m,3) dimensions at each time

i want to save these matrices in only one matrix (mr,3)

Best Answer

Try something like this:

m = 4; % Whatever you want.


r = 5; % Whatever you want.
% Preallocate the 3-D array 
% to hold all the 2-D m-by-3 matrices.
matrix3d = zeros(m, 3, r);
for k = 1 : r
  thisMatrix = rand(m, 3); % Whatever you want.
  matrix3d(:, :, k) = thisMatrix;
end

Related Solutions

MATLAB: How to multiplay matrices in different dimensions

Perhaps:

a = rand(2,2,3);
b = [2, 2; 4, 4]
% Elementwise - auto-expanding since R2016b:
r = a .* b
% Matrix multiplication:
r = zeros(2, 2, 3);
for k = 1:3
    r(:, :, k) = a(:, :, k) * b;
end

If the later is wanted, you can vectorize the code or use some tools from the FileExchange to avoid the loop.

MATLAB: Hintializing variables with different numbers and saving them in a matrix

This is asked daily for many years now. See:

The answer is always the same: Don't do this. Create an array instead and use the numbers as indices. This is faster, nicer, more flexible, easier to debug, to maintain, to expand and to read.

V = zeros(1, n);  % For scalars
m = 7;
M = zeros(m, n);  % For column vectors
C = cell(1, n);   % For variables with different sizes
for k = 1:n
  V(k)    = k ^ 2;
  M(:, k) = rand(m, 1);
  C{k}    = sprintf('%g', k);
end

Best Answer

Related Solutions

MATLAB: How to multiplay matrices in different dimensions

MATLAB: Hintializing variables with different numbers and saving them in a matrix

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