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Re: Explanation for keywords of POLY_FIT? [message #63247 is a reply to message #63137]

Thu, 30 October 2008 01:06

Karlo Janos
Messages: 31
Registered: July 2008

Member

> If your data points are X, Y and the fit is X, YFIT, then YERROR =
> stddev(Y - YFIT).

That is not correct (as I found out now), but you gave me the hint for
finding the correct answer!

YERROR is the "Root Mean Squared Error" aka the "fit standard error".
Dr. Google gives the definition. ;)

> MEASUREMENT_ERROR only influences these via changes to YFIT, but the
> form is complicated and depends on the degree of the polynomial... if
> you need the detailed expression, I'd just follow the NR derivation
> for linear least squares fit with whatever degree polynomial you need.

I assume that this is "weighted linear least squares", when using
MEASUREMENT_ERROR.

Thanks for your help!

Karlo

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[Message index]

		Explanation for keywords of POLY_FIT? By: Karlo Janos on Tue, 28 October 2008 09:41
		Re: Explanation for keywords of POLY_FIT? By: Jeremy Bailin on Wed, 29 October 2008 06:50
		Re: Explanation for keywords of POLY_FIT? By: Karlo Janos on Thu, 30 October 2008 01:06
		Re: Explanation for keywords of POLY_FIT? By: Jeremy Bailin on Thu, 30 October 2008 04:48

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