# Ramp response for transfer function using symbolic function

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Ian Thean on 6 Nov 2020
Edited: Ian Thean on 12 Nov 2020
syms s k
a = 1
b = -5/s
K = a + b;
G = 6*s + 12/s^3 + 8*s^2 + 19*s + 12;
F = 1;
R = 1/s^2;
Error = (K*G/(1+K*G*F));
ssE = limit(s*Error,s,0);
I trying to churn a ramp response figure with this code. I remove R from Error eqn as to find feedback response. I type in " figure(1);step(Error/s) " to create figure but error keeps prompting "not enough input arguements".
Could use some advice on this?
Thnk!

Raunak Gupta on 9 Nov 2020
Hi,
The step function that is used only accepts Dynamic System Models as input. One example is tf which you are trying to use. Replacing the syms s k with s = tf(‘s’) in your code clear out the error. But again limit function is only valid for symbolic expression. So, you may choose what you prefer to do.
This works fine if you want to use step.
s = tf('s');
a = 1;
b = -5/s;
K = a + b;
G = 6*s + 12/s^3 + 8*s^2 + 19*s + 12;
F = 1;
Error = (K*G/(1+K*G*F));
step(Error);
If you want to use limit, then the code given in the question works fine.
Ian Thean on 12 Nov 2020
Edited: Ian Thean on 12 Nov 2020
I see! Thanks a lot! Now I understand the difference between the two.

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