for loop in for loop not storing all variables

In the simplest way, I am trying to get 3 random (x,y) data sets per group with a total of 5 groups. (So 15 x coordinates and 15 y coordinates in total). Every time I use my mean(x) to find the average x. My for loop only calculates the mean for my groups of x coordinates. How do i do it for all 15 x coordinates?

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

h = 0.6073

h = 0.6425

h = 0.6971

h = 0.5637

h = 0.5582

Answer 1

[Walter Roberson]

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

h = 0.8827

h = 1×2

0.8827 0.2131

h = 1×3

0.8827 0.2131 0.4023

h = 1×4

0.8827 0.2131 0.4023 0.6954

h = 1×5

0.8827 0.2131 0.4023 0.6954 0.3230

mean(x,1)

ans = 1×5

0.8827 0.2131 0.4023 0.6954 0.3230

mean(x,2)

ans = 3×1

0.6141 0.5077 0.3881

You can see that if you stored all of the values, that mean(x,1) calculates the same thing as taking the mean of each column at the time you generate the column.

Answer 2

[Dameon Solestro]

Is there a way to get every x value to subtract the mean, and then place it in a matrix??

So like [(x1- mean(h) ; x2 - mean(h) ; .... ; x15-mean(h)] ??

[Walter Roberson]

In the code I posted in https://www.mathworks.com/matlabcentral/answers/1593204-for-loop-in-for-loop-not-storing-all-variables#answer_837899 then you would just use

x - mean(h)

Note that each element of your h is a mean of a column, so mean(h) would be mean of the means