Bug in Fit Report for Nlarx Models in System Identification App
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Hi
Using the System Identification App there is clearly a bug in reporting the fitting. In the Nlarx model it always returns the same fit values although they are not correct. And do not match the model NRMSE. Is this a known issue?
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1040625/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1040630/image.png)
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Answers (1)
Debraj Bhattacharjee
on 25 Jul 2022
Can you provide us the reproduction steps where you always get the same fit?
In addition, you see a different value of fit for 'Prediction' focus (as shown in the report) vs on the plot because of the difference between 'Simulation' and 'Prediction' focus. See below for more details:
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Rajiv Singh
on 9 Aug 2022
By default the estimation is performed with "prediction" focus and the response plot is computed for the "simulation" scenario. The fit numbers you see in the model display correspond to the 1-step prediction errors which is what is minimized for training the model. To train a model for simulation error minimization, do:
opt = nlarxOptions('Focus', 'simulation');
model = nlarx(data, <regressors>, opt)
Or, in the app, set the estimation focus to simulation:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1092305/image.jpeg)
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