njit-etd2003-081 - New Jersey Institute of Technology

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B.2.5 System Identification Procedure
Make sure that there is an "ident" MATLAB toolbox (Version 4.0 or later) exist in the
toolbox directory of MATLAB. The procedure described here is essentially the same as
demo #2 in iddemo. It shows an example of a typical session with the System
Identification Toolbox. First, invoke MATLAB and follow along.
1. Data have been collected from a COPD or a normal subject during one of the
experimental session. Sixty thousand data points (5 minutes) were collected. The
sampling interval is 5 ms (0.005 sec, 200sps). The data were loaded into MATLAB in
ASCII form and are now stored as the vectors hr2 (Heart Rate: output) and
rp 2 (Respiration: input) in the file agul.asc. First load the data:
load agul.asc;
2. This example selects the first 25,000 data points for building a model. For
convenience, the input-output vectors are merged into a matrix:
z2 =Ihr2 (1:25000) rp 2 (1:25000)];
Take a look at the data,
idplot(z2)
The toolbox makes frequent use of default arguments. Default values are used
when trailing arguments are omitted. In the case above, by default, all data points are
graphed and the sampling interval is one time unit.
3. One can select the values between sample numbers 10,000 and 20,000 for a closeup,
and at the same time obtain correct time scales, with
idplot(z2,10000:20000,0.005)