%% Getting Started with LTI Models -- Accessing Model Data

%   Copyright 1986-2004 The MathWorks, Inc.
%   $Revision: 1.1.6.1 $  $Date: 2004/08/17 21:33:00 $


%% Accessing Model Data
GSAccessingModelData_aux(1); % Draw figure

%%
% LTI model objects store data in a single MATLAB variable.  This data
% includes the model coefficients (i.e., A,B,C,D matrices of
% state-space models) as well as other model data,
% such as the sample time or the input and output names.
%
% There are several ways to access the data:
%
% * The SET / GET commands
% * Direct structure referencing
% * Data retrieval commands

%% Accessing Model Data with SET / GET
GSAccessingModelData_aux(2); % Draw figure

%%
% You can use the SET command to modify model data:
%
%  >> set(sys,PropertyName,PropertyValue)
%
% Conversely, you can use the GET command to retrieve model data:
%
% >> PropertyValue = get(sys,PropertyName)
%
% The illustration above shows how to use SET and GET to modify and
% retrieve the gain value of a zero-pole-gain model.


%% Accessing Model Data with Direct Structure Referencing
GSAccessingModelData_aux(3); % Draw figure

 
%%
% You can also modify and retrieve model data directly by structure
% referencing:
% 
% >> sys.PropertyName = PropertyValue         % equivalent to SET
%
% >> PropertyValue = sys.PropertyName         % equivalent to GET
%
% The illustration above shows how this technique parallels the use of the
% SET and GET commands.
 

%% Data Retrieval (Quick Access)
GSAccessingModelData_aux(4); % Draw figure

 
%%
% You can quickly retrieve model data with the following commands:
%
% >> [num,den,Ts] = tfdata(sys)
%
% >> [z,p,k,Ts] = zpkdata(sys)
%
% >> [a,b,c,d,Ts] = ssdata(sys)
%
% >> [response,freq,Ts] = frdata(sysfr)
%
% Note that the FRDATA command is specific to *FRD* models, but you can use
% TFDATA, ZPKDATA, and SSDATA with any *TF*, *ZPK*, or *SS* model.
 
 
%%
% The commands TFDATA and ZPKDATA return some of their data (num,den,z,p)
% in cell arrays in order to facilitate data retrieval for MIMO models and 
% model arrays.
%
% For a single SISO model, you can use a second input argument 'v' to
% specify that these commands return data in vectors rather than cell 
% arrays:
%
% >> [num,den,Ts] = tfdata(sys,'v')
%
% >> [z,p,k,Ts] = zpkdata(sys,'v')