User`s guide

Transforming Between Time- and Frequency-Do main Data
Transforming Frequency-Domain Data
In the System Identification To ol GUI, frequency -domain data has an icon
with a green background. You can trans form frequency-domain data to
time-domain or frequency-response (frequency-function) data.
Transformin g from time-dom ain or frequency-dom ain data to
frequency-response data is equivalent to estimating a nonparametric model of
the data using the
spafdr method.
1 In the System Identification Tool GUI, drag the icon of the data you want
to transform to the Working Data rectangle.
2 Select <–Preprocess > Transform data.
3 In the Transform to list, select one of the following:
•
Frequency Fu ncti on —Createanewidfrd object using the s pafd r
method. Gotostep4.
•
Time Domain Data —Createanewid data object using the ifft
(inverse fast Fourier transform) method. Go to step 6.
4 In the Frequency Spacing list, select the spacing of the frequencies at
which the frequency function is estimated:
•
linear — Uniform spacing of frequency values between the endpoints.
•
logarithmic — Base-10 logarithmic spacing of frequency values
between the endpoints.
5 In the Number of Frequencies field, enter the number of frequency
values.
6 In the Name of new data field, type the name of the new data set. This
name must be unique in the Data Board.
7 Click Transform to add the new data set to the Data B oard in the System
Identification Tool GUI.
8 Click Close to close the Transform Data dialog box.
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