Why do I need to declare a variable inside a nested 'for' loop?
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Commented: Ted Baker on 22 Oct 2019
Hi, I have some code, below, which fails on the last line before both 'end's (T_noise_out(it) = ....). The Command Window tells me that this is due to T_noise_out being an unrecognised variable. However, just a few lines above it, I am able to use 'F_noise_in(term_num)' and 'F_noise_out(term_num)' without explicitly declaring them. Why is this? I anticipated that this code would create an array of complex numbers called T_noise_out.
for term_num = 1: 2: nterms
fprintf('Processing term %g of %g \n', term_num, nterms);
%Add new Fourier coefficient
F_noise_in(term_num) = -i*4/(pi*term_num);
F_noise_out(term_num) = F_noise_in(term_num).*H(term_num);
for it = 1: 1: ntsamples
t = (it-1).*dt;
real_F_noise_out = real(F_noise_out(term_num));
imag_F_noise_out = imag(F_noise_out(term_num));
T_noise_out(it) = T_noise_out(it)+real_F_noise_out*cos(2*pi*f0*term_num*t)-imag_F_noise_out*sin(2*pi*f0*term_num*t);
Adam on 22 Oct 2019
Edited: Adam on 22 Oct 2019
You are referring to it on the right-hand side of the equation as well as on the left. First time round it does not exist yet so that will error. You would need to initialise it before your outer loop to contain 0s of the correct size if you intend to store a running sum in it.
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