Why this piece of code gives error?

Question

Sadiq Akbar 2023-2-28

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https://ww2.mathworks.cn/matlabcentral/answers/1920135-why-this-piece-of-code-gives-error

评论： Sadiq Akbar 2023-2-28

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
wd = steervec(getElementPosition(ula)/lambda,thetaad);
% 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);

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Answer 1

Anton Kogios 2023-2-28

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在 MATLAB Online 中打开

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 2023-2-28

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 2023-2-28