%% Create Fully Specified Model
% Create the ARIMA(2,1,1) model represented by this equation:
% (1+0.5L^2)(1-L)y_t=3.1+(1-0.2L)\varepsilon_t,
% where \varepsilon_t is a series of iid Gaussian random variables. Use the longhand syntax to specify parameter values in the equation written in difference-equation notation:
% \Delta y_t = 3.1 - 0.5\Delta y_{t-2}
%  +\varepsilon_t - 0.2\varepsilon_{t-1}.

Mdl = arima('ARLags',2,'AR',-0.5,'D',1,'MA',-0.2,...
    'Constant',3.1)

% Mdl is a fully specified arima object because all its parameters are known. You can pass Mdl to any arima object function except estimate. For example, plot the impulse response function of the model for 24 periods by using impulse.

impulse(Mdl,24)

% Copyright 2019 The MathWorks, Inc.