nlarx is not working at all

Hello,

I have tried to excute the example code named "Estimate Nonlinear ARX Model" for nlarx (Estimate parameters of nonlinear ARX model - MATLAB nlarx - MathWorks France) but the nlarx command is not working. The error message is the following: "too many inputs). I've tried to reduced the size of the data set but it has not worked....

Could you please help me? I don't understand why the example code isn't running correctly....

Thanks,

Elodie

Answer 1

[Star Strider]

Check to see if you have another function (or something else) with the same name.

To do that, run this:

which nlarx -all

from your Command Window or a script.

The correct result should be something like this:

which nlarx -all

/MATLAB/toolbox/ident/nlident/nlarx.m

If it returns anything else, that will point to the problem.

Meanwhile, that example works here —

load twotankdata;

Ts = 0.2;
z = iddata(y,u,Ts);

sysNL = nlarx(z,[4 4 1])

sysNL =

Nonlinear ARX model with 1 output and 1 input
  Inputs: u1
  Outputs: y1

Regressors:
  Linear regressors in variables y1, u1

Output function: Wavelet network with 11 units
Sample time: 0.2 seconds

Status:                                          
Estimated using NLARX on time domain data "z".   
Fit to estimation data: 96.84% (prediction focus)
FPE: 3.482e-05, MSE: 3.431e-05                   
More information in model's "Report" property.

sysL = arx(z,[4 4 1]);

figure
compare(z,sysNL,sysL)

.

[Elodie]

Thank you very much for your answer! The problem was actually as you said : I have a linear polynomial model already named "nlarx" in my Workspace because of System Identification toolbox and that prevents from working the mentionned example.

Everything is working now!

Thanks a lot and sorry for disturbing you with so simple problem...

[Star Strider]

As always, my pleasure!

Absolutely no apologies necessary! It is actually a common problem, and one that many of us (including me) have made over the years.

[Nikolas Anastasiadis]

Hi!

I have a similar problem, but nothing seems to have the same name in the workspace.

I tried what you suggested and I still get this:

Any idea for where the problem might be?

[Star Strider]

You obviously have the function, and the call looks to me to be correct.

I have no ideas what the problem is, so it would be best for you to Contact Support and include the URL of your Comment here in your note to them.

.

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