How to compute poles-zeros using matlab?

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Li Hui Chew 2021-7-18

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https://ww2.mathworks.cn/matlabcentral/answers/880913-how-to-compute-poles-zeros-using-matlab

回答： Mathieu NOE 2021-7-19

H(z)=(1-2^-2)/(1-0.9*z^-1+0.6*z^-2+0.5*z^-3)
b=[1 0 -1 0];
a=[1 0.9 0.6 0.5];
% to find zeors
zeros=roots(b)
% to find poles 
poles=roots(a)
% to plot 
zplane(b,a)

Is my approach correct?

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Answer 1

Mathieu NOE 2021-7-19

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https://ww2.mathworks.cn/matlabcentral/answers/880913-how-to-compute-poles-zeros-using-matlab#answer_749553

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hello

I hope the coefficient in b and a are correct (then the zeros and poles are inside the unit circle ) , because the first line is not 100% matching the coefficients you declared in b and a :

H(z)=(1-2^-2)/(1-0.9*z^-1+0.6*z^-2+0.5*z^-3) should be then replaced by :

H(z)=(1-z^-2)/(1+0.9*z^-1+0.6*z^-2+0.5*z^-3)

otherwise the zeros and pole computation is correct , and there is also this method (FYI) :