Transform Frequency-Domain Data in the App

In the System Identification app, frequency-domain data has an icon with a green background. You can transform frequency-domain data to time-domain or frequency-response (frequency-function) data.

Transforming from time-domain or frequency-domain data to frequency-response data is equivalent to estimating a nonparametric model of the data using the spafdr method.

  1. In the System Identification app, 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 Function — Create a new idfrd object using the spafdr method. Go to step 4.

    • Time Domain Data — Create a new iddata 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 Board in the System Identification app.

  8. Click Close to close the Transform Data dialog box.

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