I need help with a for loop that gives me an assignment error.

Hi all, I'm a beginner to Matlab but I have this code:

clear

clc

X_nf=randi([10 50],1,10);

sigma_x=rand(1,10);

N=numel(X_nf);

V=zeros(length(X_nf),10);

for i=1:10

V(i)=X_nf+sigma_x.*randn(1,N)

end

and it is giving me this error: In an assignment A(:) = B, the number of elements in A and B must be the same. I would like it to create the variable V that has a 10x10 matrix of numbers that are varied a little bit from the variable X_nf with the random noise I am adding.

Any help would be great. Thanks!

Answer 1

[sloppydisk]

When you get this kind of error you want to look at the line (11 in this case) and check the sizes of the different variables. So let's look at

size(V(i))
size(X_nf)
size(sigma_x.*randn(1,N))

Now we see that V(i) is just a 1x1, while the others are 1x10. So instead we should probably write:

V(i, :) = X_nf+sigma_x.*randn(1,N)

This indexes the i-th row instead of just the i-th element.

[Barbara Wortham]

Thanks! Life Saver!