why the results are different? residue & residuez

A=[1 -1.9 1.19 -0.281 0.018];
B=[5 -10.57 9.95 -3.5 0];
[r,p,k]=residue(B,A)
[r1,p1,k1]=residuez(B,A)
The correct result can be obtained when using residue. But I'm trying to figure why residuez couldn't and hot to make it work?
I assuming it has something to do with the last term in B "0". When I removed 0 then using residue, the result will be same as residuez.

2 Comments

There are similarities between 'residue' function and 'residuez' function but the primary area of application of these two functions is different. The 'residue' function computes the partial fraction expansion of continuous-time systems in the Laplace domain, whereas the 'residuez' function does it for discrete-time systems in the z-domain.
You can refer to the following links to better understand how these two functions work: https://in.mathworks.com/help/matlab/ref/residue.html https://in.mathworks.com/help/signal/ref/residuez.html#bqigqq_-1
Yes, you will have problems in verification of your mathematically computed PFE in z-domain if you use residuez function however it would match if you use residue function. Main problem is residue function does what we do in mathematics while residuez computes PFE w.r.t. z^{-1}.

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on 2 Jun 2017

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