User`s guide

6 Time Series Model Identification
Estimating Time-Series Power Spectra
In this section...
“How to Estimate T ime-Series Power Spectra Using the GU I” on page 6-4
“How to Estimate Time-Series Pow er Spectra at the Command Line” on
page 6-5
How to Estimate Time-Series Power Spectra Using
the GUI
You must h ave already imported your data into the GUI, as described in
“Preparing Time-Series Data” on page 6-3.
To estimate time-series spectral models in the System Identification Tool GUI:
1 In the S ystem Identification Tool GUI, select Estimate > Spectral
models to open the Spectral Model dialog box.
2 In the Method list, select the spectral analysis method you w ant to use.
For information about each me tho d, see “Options for Computing Spectral
Models” on page 3-5.
3 Specify the f
requencies at which to compute the spectral m odel in either of
the followin
gways:
• In the Freque
ncies field, ente r either a vector of values, a MATLAB
expression
that evaluates to a vector, or a variable name of a vector in
the M ATLAB w
orkspace. For example,
logspace(-1,2,500).
• Use the comb
ination of Frequency Spacing and Frequencies to
construct t
he frequency vector of values:
– In the Frequ
ency Spacing list, select
Linear or Logarithmic
frequency s
pacing.
Note For etf
e
,onlytheLinear option is available.
– In the Frequ
encies field, enter the number of frequency points.
6-4