Correct me if I am wrong but i think "lsim" works for both continuous (S Domain) and discrete (Z Domain) transfer functions.
"The command lsim(sys,U,T,X0) plots the time response of a linear time-invariant system. This system can be continuous or discrete. For a continuous-time system, the differential equation is integrated from time T(0) to T(length(T)), starting at the initial condition X0 and using the input U. The input vector must have the same number of entries as the time vector. If the initial conditions are all zero, X0 may be omitted.
For a discrete-time system, U should be sampled at the same rate as the system (T is then redundant and may be omitted or set to the empty matrix, i.e. [ ])."
