[SciPy-user] curve_fit step-size and optimal parameters

Stéfan van der Walt stefan@sun.ac...
Mon Jun 8 15:15:30 CDT 2009


2009/6/8 Robert Kern <robert.kern@gmail.com>:
> On Mon, Jun 8, 2009 at 14:59, ElMickerino<elmickerino@hotmail.com> wrote:
>> My question is, how can I get curve_fit to use a very small step-size for
>> the phase, or put in strict limits, and to therefore get a robust fit.  I
>> don't want to tune the phase by hand for each of my 60+ datasets.
>
> You really can't. I recommend the A*sin(w*t)+B*cos(w*t)
> parameterization rather than the A*sin(w*t+phi) one.

Could you expand?  I can't immediately see why the second
parametrisation is bad.  Can't a person do this fit using non-linear
least-squares?  Ah, that's probably why you use the other
parametrisation, so that you don't have to use non-linear least
squares?

Regards
Stéfan


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