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# How to input transfer function without simplifying it?

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Supermankid on 12 Sep 2017
Answered: Teja Muppirala on 13 Sep 2017
Hi everyone,
Normally, we can give numerator = [ 1 0]; denominator =[1 1 4]; and system1=tf(num,den); but if the transfer function is like:
G(s) = {s + 2}/{s(s − 1)(s + 6)^2}
can I add this transfer function without simpligying (I mean without multiplying the denominators)
=> only from s(s-1)(s+6)^2
May be someone can provide some tips.
##### 1 CommentShowHide None
Walter Roberson on 12 Sep 2017
G = tf([1 2],[1 0]) * tf(1,[1 -1]) * tf(1, [1 6])^2

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### Accepted Answer

Teja Muppirala on 13 Sep 2017
s = tf('s')
G = (s+2)/(s*(s-1)*(s+6)^2)
This gives a transfer function (tf) with the polynomials expanded
G =
s + 2
----------------------------
s^4 + 11 s^3 + 24 s^2 - 36 s
Or you can express it as a ZPK (zero-pole-gain)
G = zpk((s+2)/(s*(s-1)*(s+6)^2))
Then you get
G =
(s+2)
---------------
s (s+6)^2 (s-1)
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