User`s guide

Analyzing Data Quality Using Plots
Analyzing Data Quality Using Plots
In this section...
“Supported Data Plots” on page 1-75
“Plotting Data in the System Identification Tool GUI” on page 1-75
“Plotting Data at the Command Line” on page 1-81
Supported Data Plots
You c an create the following plo ts of your data:
• Time plot — Shows data values as a function of time.
• 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 sampling interval.
• Frequency-response plot — For frequency-response data, s hows the
amplitude and phase of the frequency-response function on a Bode plot. For
time- and frequency-domain data, s hows the empirical transfer function
estimate (see
etfe).
The plots you create using the System Identification To ol GUI provide
options that are specific to the System Identification Toolbox product, such
as selecting specific channel pairs in a m ultiv ariate signa ls or converting
frequency units between Hertz and radians per second.
Theplotsyoucreateusingtheplotcommands,suchas
plot, bode,andffplot,
are displayed in the standard MATLA B Figure window, which provides
options for formatting, saving, printing, and exporting plots to a variety of file
formats. For more information, see the MA TLAB Graphics documentation.
Plotting Data in the System Identification Tool GUI
• “How to Plot D ata in the G UI” on page 1-76
• “Working with a Time Plot” on page 1-77
• “Working with a Data Spectra Plot” on page 1-78
1-75