# Implementing factored form in MATLAB?

2 views (last 30 days)
ABTJ on 10 Mar 2021
Commented: Walter Roberson on 10 Mar 2021
I have a z transform in rational form as shown in attached photo
and i want to convert it into factored form
How can i implement it in MATLAB? I learnt from a google resource that we should use "zp2sos"command but i am not satisfied because output of "zp2sos"command does not looks like factored form
Walter Roberson on 10 Mar 2021
By the way, you do not need to create an zpk intermediate form
z = tf('z');
H = (4*z^2+3*z+9)/(4*z^2+3*z-4)
H = 4 z^2 + 3 z + 9 --------------- 4 z^2 + 3 z - 4 Sample time: unspecified Discrete-time transfer function.
H = [H, z/H] %just to give a more complicated system
H = From input 1 to output: 4 z^2 + 3 z + 9 --------------- 4 z^2 + 3 z - 4 From input 2 to output: 4 z^3 + 3 z^2 - 4 z ------------------- 4 z^2 + 3 z + 9 Sample time: unspecified Discrete-time transfer function.
HN = H.Numerator;
HD = H.Denominator;
HN = cellfun(@(C) C(find(C,1):end), HN, 'uniform', 0); %trim leading 0
HD = cellfun(@(C) C(find(C,1):end), HD, 'uniform', 0); %trim leading 0
Hsos = cellfun(@tf2sos, HN, HD, 'uniform', 0).';
celldisp(Hsos)
Hsos{1} = 1.0000 0.7500 2.2500 1.0000 0.7500 -1.0000 Hsos{2} = 1.0000 0.7500 -1.0000 1.0000 0.7500 2.2500

R2015a

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