STEP  Step response of LTI models.
 
    STEP(SYS) plots the step response of the LTI model SYS (created 
    with either TF, ZPK, or SS).  For multi-input models, independent
    step commands are applied to each input channel.  The time range 
    and number of points are chosen automatically.
 
    STEP(SYS,TFINAL) simulates the step response from t=0 to the 
    final time t=TFINAL.  For discrete-time models with unspecified 
    sampling time, TFINAL is interpreted as the number of samples.
 
    STEP(SYS,T) uses the user-supplied time vector T for simulation. 
    For discrete-time models, T should be of the form  Ti:Ts:Tf 
    where Ts is the sample time.  For continuous-time models,
    T should be of the form  Ti:dt:Tf  where dt will become the sample 
    time for the discrete approximation to the continuous system.  The
    step input is always assumed to start at t=0 (regardless of Ti).
 
    STEP(SYS1,SYS2,...,T) plots the step response of multiple LTI
    models SYS1,SYS2,... on a single plot.  The time vector T is 
    optional.  You can also specify a color, line style, and marker 
    for each system, as in 
       step(sys1,'r',sys2,'y--',sys3,'gx').
 
    When invoked with left-hand arguments,
       [Y,T] = STEP(SYS)
    returns the output response Y and the time vector T used for 
    simulation.  No plot is drawn on the screen.  If SYS has NY
    outputs and NU inputs, and LT=length(T), Y is an array of
    size [LT NY NU] where Y(:,:,j) gives the step response of the 
    j-th input channel.
 
    For state-space models, 
       [Y,T,X] = STEP(SYS) 
    also returns the state trajectory X which is an LT-by-NX-by-NU
    array if SYS has NX states.
 
    See also IMPULSE, INITIAL, LSIM, LTIVIEW, LTIMODELS.

 Overloaded methods
    help lti/step.m
    help frd/step.m