FAQ

Upgrading

How do I upgrade to a newer version?

Delete your old toolbox directory and replace it by the new one.

Using

I want to model my own problem

See the Adding an example page.

I want to contribute some data/patch/documentation/...

See the Contributing page.

How do I interface with the toolbox?

See the Data format page.

Troubleshooting

I have a problem and I want to report it

See the Reporting problems page.

I sometimes get flat models when using rational functions

The PolynomialModel tries to do a least squares fit, based on which monomials are allowed in numerator and denominator. We have experienced that some models just find a flat model as the best least squares fit. There are two causes for this:

1. The number of sample points is few, and the model parameters (as explained here and here) force the model to use only a very small set of degrees of freedom. The solution in this case is to increase the minimum percentage bound in the xxxPolynomialInterface section of your configuration file. Set the percentageBounds option to 100,100 to force the polynomial models to exactly interpolate.
2. Another possibility is that given a set of monomial degrees, the flat function is just the best possible least squares fit. In that case you simply need to wait for more samples.

There is no noise in my data yet the rational functions don't interpolate

See the previous question.

When using rational functions I sometimes get 'spkies' (poles) in my model

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