How to Plot Residuals in the App

To create a residual analysis plot for parametric linear and nonlinear models in the System Identification app, select the Model resids check box in the Model Views area. For general information about creating and working with plots, see Working with Plots.

To include or exclude a model on the plot, click the corresponding model icon in the System Identification app. Active models display a thick line inside the Model Board icon.

The following table summarizes the Residual Analysis plot settings.

Residual Analysis Plot Settings

ActionCommand

Display confidence intervals around zero.

Note

Confidence internal are not available for nonlinear ARX and Hammerstein-Wiener models.

  • To display the dashed lines on either side of the nominal model curve, select Options > Show confidence intervals. Select this option again to hide the confidence intervals.

  • To change the confidence value, select Options > Set % confidence level and choose a value from the list.

  • To enter your own confidence level, select Options > Set confidence level > Other. Enter the value as a probability (between 0 and 1) or as the number of standard deviations of a Gaussian distribution.

Change the number of lags (data samples) for which to compute autocorrelation and cross-correlation functions.

Note

For frequency-domain validation data, increasing the number of lags increases the frequency resolution of the residual spectrum and the transfer function.

  • Select Options > Number of lags and choose the value from the list.

  • To enter your own lag value, select Options > Set confidence level > Other. Enter the value as the number of data samples.

(Multiple-output system only)
Select a different input-output pair.

Select the input-output by name in the Channel menu.

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