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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Debraj Bhattacharjee
2022-7-25
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
2022-8-9
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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