# Why this piece of code gives error?

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Sadiq Akbar on 28 Feb 2023
Commented: Sadiq Akbar on 28 Feb 2023
When I run the following code, it gives me error on line 19. The code is:
clear;clc;
c = 3e8; % signal propagation speed
fc = 1e9; % signal carrier frequency
lambda = c/fc; % wavelength
thetaad = -30:5:30; % look directions
thetaan = [-40 40]; % interference direction
ula = phased.ULA(10,lambda/2);
ula.Element.BackBaffled = true;
% Calculate the steering vector for null directions
wn = steervec(getElementPosition(ula)/lambda,thetaan);
% Calculate the steering vectors for lookout directions
% Compute the response of desired steering at null direction
rn = wn'*wd/(wn'*wn);
% Sidelobe canceler - remove the response at null direction
w = wd-wn*rn;
% Plot the pattern
pattern(ula,fc,-180:180,0,'PropagationSpeed',c,'Type','powerdb',...
'CoordinateSystem','rectangular','Weights',w);
hold on; legend off;
The error is:
Error using /
Matrix dimensions must agree.
Error in abc (line 19)
rn = wn'*wd/(wn'*wn);

Anton Kogios on 28 Feb 2023
Your multiplications in Line 19 give a 2 by 13 matrix in the numerator and a 2 by 2 matrix in the demoninator.
To perform matrix multiplication/division, you need the number of columns of the first to be equal to the number of rows of the second. So, a fix to your error may be this, but it depends what you are trying to do:
rn = (wn'*wd)'/(wn'*wn);
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Anton Kogios on 28 Feb 2023
Sorry Sadiq, I wish I could help further but I am not too familar with the content of your question. Hopefully someone else is able to help out.
I did notice, however, that since you turn hold on, you can just run the code twice with each separate value, so maybe you can create a loop and function to meet your needs.
Sadiq Akbar on 28 Feb 2023
Thanks a lot for your kind response dear Anton Kogios. Yes, you are right. May be someone else may help me out. Thanks once again.