How do can I use every number in my loop?

So right now I have 3 groups of 5 x values(15 x values in total. How do I perform a loop where I use the values after I get the mean?? so how would i create a matrix such that . M= [x1-Mean_allx ; x2-Mean_allx ; x3-Mean_allx ;...... ; x15-Mean_allx] ?? Could it also be possible for the value to be Matrix to be averaged?

for j=1:3
    for i=1:5
        x(i,j)= rand()
    
        hold on
    end
    hold on
    h(j)=mean(x(:,j))
    Mean_allx= mean(h)
    
  

end

Answer 1

[Walter Roberson]

for j=1:3
    for i=1:5
        x(i,j)= rand()
    end
    h(j)=mean(x(:,j))
end
Mean_allx= mean(h)

Answer 2

[the cyclist]

% Set the random number seed, for reproducibility
rng default

% Create the x data
x = rand(3,5);

% Mean of all the x data
Mean_allx = mean(x,'all');

% Subtract the mean from the x data
x_minus_mean = x - Mean_allx;

[Dameon Solestro]

I kind of need both i and j loops.. is there a way for this to still be possible??