How to randomly change element of matrix?

I have an n×n matrix.

I want to randomly change the element of A at random position.

The element of matrix can be from 0 to 1000

I used randi(1000) for random entry

I want to repeat this process 100 times to get 100 new matrices and save all these matrices in a separate folder

for i= 1:I00

Answer 1

[the cyclist]

I'll illustrate for an nxn where n = 3, and repeat 2 times:

% Set the random number generator seed, for repeatability here
rng default

% Size of matrix
n = 3;

% Starting matrix -- use your real data instead
M = magic(n);

% Loop two times
for ii = 1:2
    % Chose random element index (using linear index)
    rndIdx = randi(n*n);
    % Change the random element to a random value from 1:1000 (which I guess is what you want?)
    M(rndIdx) = randi(1000)
    % Put save step here, if you want to save each one
end

M = 3×3

8 1 6 3 5 906 4 9 2

M = 3×3

8 1 6 914 5 906 4 9 2

This code keep going forward from the original matrix, changing elements one at a time (but sometimes it could overwrite the same location more than once). You'll need to adjust the code if you want to start from M, save, start from original M again, etc.

But hopefully you get the idea.

[Ammy]

Thank you very much

[the cyclist]

% Set the random number generator seed, for repeatability here
rng default

% Size of matrix
n = 3;

% Starting matrix -- use your real data instead
M = magic(n);

% Loop two times
for ii = 1:2
    % Chose random element index (using linear index)
    rndIdx = randi(n*n);
    % Change the random element to a random value from 1:1000 (which I guess is what you want?)
    Mnew = M;
    Mnew(rndIdx) = randi(1000)
    % Put save step here, if you want to save each one
end

Mnew = 3×3

8 1 6 3 5 906 4 9 2

Mnew = 3×3

8 1 6 914 5 7 4 9 2

[Ammy]

Thank you very much.

Answer 2

[Fabio Freschi]

You can use linear indexing

% your matrix
A = rand(10,100);

% create the folder
mkdir('storage');

% loop
for i = 1:100
    % random matrix
    Arand(randi(numel(A))) = rand;
    % save
    save(strcat('./storage/mymatrix',num2str(i),'.mat'));
end

[Jan]

Or randi(1000) instead if rand().

[Ammy]

Thank you very much.