MATLAB: Matlab extract coefficient from z transform function

ztransform

Hi I have a z transform function 3/z + 5/z^2 + 6/z^3 + 1

How would I extract the coefficients from this equation? I have tried using coeffs and it says it is not a polynomial.

I would like the answer to come out as [3 5 6 1]

The symbolic z variable is declared as syms z

Best Answer

Use the sym2poly function, although here it’s necesary to do an intermediate step:

syms z 
fz = 3/z + 5/z^2 + 6/z^3 + 1
[fzn, fzd] = numden(fz)
fzc = sym2poly(fzn)
fzc = circshift(fzc, [0 -1])

produces:

fzc =
       3     5     6     1

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Easiest:

syms z 
P(z) = z.^9 + z.^8 - z.^7 + z.^6 - z.^5 + z + 1; 
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Otherwise:

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With the same essential result.

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