for loop in for loop not storing all variables

Question

Dameon Solestro 2021-11-22

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1593204-for-loop-in-for-loop-not-storing-all-variables

评论： Walter Roberson 2021-11-24

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

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Answer 1

Walter Roberson 2021-11-23

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1593204-for-loop-in-for-loop-not-storing-all-variables#answer_837899

在 MATLAB Online 中打开

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.