Before you start estimating models from data, you should check your data for the presence of any undesirable characteristics. For example, you might plot the data to identify drifts and outliers. You plot analysis might lead you to preprocess your data before model estimation.
The following data plots are available in the toolbox:
Time plot — Shows data values as a function of time.
You can infer time delays from time plots, which are required inputs to most parametric models. A time delay is the time interval between the change in input and the corresponding change in output.
Spectral plot — Shows a periodogram that is computed by taking the absolute squares of the Fourier transforms of the data, dividing by the number of data points, and multiplying by the sample time.
Frequency-response plot — For frequency-response
data, shows the amplitude and phase of the frequency-response function
on a Bode plot. For time- and frequency-domain data, shows the empirical
transfer function estimate (see