User`s guide

Transforming Between Time- and Frequency-Do main Data
frequencies, and also make the frequency vector coarser in the region outside
the system dynamics. Typically, high-frequency noise dominates away
from freque n c ies where interesting system dynam ics occur. The System
Identification Tool GU I lets you specify logarithmic frequency spacing, which
results in a variable frequency resolution.
Note The spafdr command lets you lets you specify any variable frequency
resolution.
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 Do main Data —Createanewiddata object. Gotostep6.
•
Frequency Fu ncti on —Createanewidfrd o bject with different
resolution (number and spacing of frequencies) using the
spafdr method.
Go to step 4.
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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