why am I getting the following error?

s = tf('s')

'tf' requires one of the following:

Control System Toolbox

DSP System Toolbox

Model Predictive Control Toolbox

Signal Processing Toolbox

Answer 1

[Abdo Zayet]

clear all; %% FIRST TRANSFER FUNCTION G1: A1=[1 3 2 5]; B1=[0 1]; C1=[1 2]; G1=tf('num1','den1'); %%SECOND TRANSFER FUNCTION G2: A2=[-4 0 0 3]; B2=[1 0]; C2=[3 0]; G2=tf('num2','den2'); %%THIRD TRANSFER FUNCTION H: A3=[3 2 1 0]; B3=[1 1]; C3=[1 1]; H=tf('num3','den3'); %%GENERAL TRANSFER FUNCTION G: G1H=feedback(G1,H); G=series(G1H,G2)