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    %% Query Model Characteristics
% This example shows how to query model characteristics such as stability,
% time domain, and number of inputs and outputs.  You can use the techniques of
% this example on any type of dynamic system model.
%%
% Load a saved state-space (<docid:control_ref.f4-390421>) model.
load(fullfile(matlabroot,'examples','control','queryexample.mat'),'T')
%%
% Query whether |T| has stable dynamics.
Bstab = isstable(T)
%%
% The |isstable| command returns 1 (|true|) if all system poles are in the
% open left-half plane (for continuous-time models) or inside the open unit
% disk (for discrete-time models). Otherwise, |isstable| command returns 0
% (|false|).  Here, the result shows that the model is stable.
%%
% Query whether |T| has time delays.
Bdel = hasdelay(T)
%%
% The returned value, 1, indicates that |T| has a time delay. For a
% state-space model, time delay can be stored as input delay, output delay,
% internal delay, or a combination. Use |get(T)| to determine which
% properties of |T| hold the time delay, and use dot notation to access the
% delay values.  The |hasInternalDelay| command tells you whether there is
% any internal delay.
%%
% Query whether |T| is proper.
Bprop = isproper(T)
%%
% The returned value indicates that the system has relative degree less
% than or equal to 0. This is true of a SISO system when it can be
% represented as a transfer function in which the degree of the numerator
% does not exceed the degree of the denominator.
%%
% Query the order of |T|.
N = order(T)
%%
% For a state-space model, |order| returns the number of states, which is 5
% in this case.  For a |tf| or |zpk| model, the order is the number of
% states required for a state-space realization of the system. 
%%
% Query whether |T| is a discrete-time system.
Bdisc = isdt(T)
%%
% The returned value indicates that |T| is
% a discrete-time model. Similarly, use |isct| to query whether |T| is
% a continuous-time model.
%% 
% Load a MIMO model and query the input/output dimensions.
load(fullfile(matlabroot,'examples','control','queryexample.mat'),'Tmimo')
ios = iosize(Tmimo)
%% 
% In the resulting array, the number of outputs is first.  Therefore,
% |Tmimo| has 4 inputs and 7 outputs.