Re: Polyfit with scaling

[Dmitri A. Sergatskov]

On Jan 30, 2008 11:19 AM, Thomas Weber <address@hidden> wrote:
> I'd like to propose the attached patch for polyfit.m
> It introduces an optional fourth bool parameter 'scale'. If not set, or
> if it's set to 'false', nothing changes.
>
> If it's set to true, the x values are scaled by their maximal absolute
> value prior to calculating the polynomial coefficients. This has a
> stabilizing effect on the calculation.
>

I do not understand why this change had not been made a long time ago
-- we had few reports of faulty fits. I think the better
scaling is:

x = (x-mean(x))/std(x).

wpolyfit from octave-forge does the scaling like that.


>         Thomas
>


Dmitri.
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