Re: Polyfit with scaling

[Ben Abbott]

On Feb 4, 2008, at 5:04 AM, Thomas Weber wrote:

> Am Sonntag, den 03.02.2008, 19:20 -0500 schrieb Ben Abbott:
>
> > Give these results and the need to remain compatible with past
> > expectations, and with Matlab, I'm inclined to make both QR and
> > normalization optional.
>
> Why do we need to stay compatible with past expectations? If polyfit
> gets better with fitting, I don't think anybody would mind.

You've missed my point. The expectations I refer to are the  
consistency of outputs, and compatibility of functionality. By  
compatibility, I do not mean to copy its bugs and/or weaknesses.

> With regards to Matlab, it uses a QR decomposition
> http://www.mathworks.com/access/helpdesk/help/techdoc/ref/polyfit.html

Thanks! Looking over that document, it appears to explain the intent  
of the Cholesky factor of the Vandermonde matrix. In addition, it  
implies that Mathworks normalizes their data as well.

I have a version of polyfit that does all these things. I'll clean it  
up, do some comparative testing with Matlab and post it for review  
latter.

Ben