%% Discrete-Time Transfer Function Model Using Rational Expression
% For this example, create a discrete-time transfer function model using a rational expression. Using a rational expression can sometimes be easier and more intuitive than specifying polynomial coefficients.
% Consider the following system:
% sys(z) = \frac{z-1}{z^2-1.85z+0.9}.
% To create the transfer function model, first specify z as a tf object and the sample time Ts.

ts = 0.1;
z = tf('z',ts)

%
% Create the transfer function model using z in the rational expression.

sys = (z - 1) / (z^2 - 1.85*z + 0.9)

% Copyright 2018 The MathWorks, Inc.