Continuous-time models can be specified in one of three forms: state space (ss), transfer function (tf), and zero-pole gain (zpk).
The commands for forming these models are
sys = ss(a,b,c,d) % state space sys = tf(num,den) % transfer function sys = zpk(z,p,k) % zero-pole-gain
where sys is the desired name of the model formed in each case. The a,b,c,d terms are the state space matrices. The num and den terms are vectors of polynomial coefficients, in decending order of powers in s. The z and p terms are row vectors of zero and pole locations (roots of numerator and denominator polynomials, respectively), while k is the gain term (note that this is not necessarily equal to the gain of the transfer function ...