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Transform Time-Domain Data in the App

In the System Identification app, time-domain data has an icon with a white background. You can transform time-domain data to frequency-domain or frequency-response data. The frequency values of the resulting frequency vector range from0to the Nyquist frequency f S = π T s , whereTsis the sample time.

Transforming from time-domain to frequency-response data is equivalent to estimating a model from the data using thespafdrmethod.

  1. In the System Identification app, drag the icon of the data you want to transform to theWorking Datarectangle.

  2. In theOperationsarea, select<--Preprocess>Transform datain the drop-down menu to open the Transform Data dialog box.

  3. In theTransform tolist, select one of the following:

    • Frequency Function— Create a newidfrdobject using thespafdrmethod. Go to step 4.

    • Frequency Domain Data— Create a newiddataobject using thefftmethod. Go to step 6.

  4. In theFrequency Spacinglist, 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 theNumber of Frequenciesfield, enter the number of frequency values.

  6. In theName of new datafield, type the name of the new data set. This name must be unique in the Data Board.

  7. ClickTransformto add the new data set to the Data Board in the System Identification app.

  8. ClickCloseto close the Transform Data dialog box.

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