[S] Determining coefficients from Curve Fitting Plot

Howard, Cheryl (Cheryl.Howard@Thomson.com)
Fri, 30 Oct 1998 11:14:44 -0500


Given that I've found a good visual fit to my data using a Curve Fitting
Plot is there an easy way to determine the coefficients of the equation
that was fit?

I'm using S-Plus 4.5 under Windows 95.

I used a polynomial fit (from the 2-D plot palette) with the following
parameters on the Curve Fitting tab:
Curve Fit Type = Power
Poly. Order = 3

I assume the resulting equation is something like

y = a * x ^ (b + c * ln(x) + d * (ln(x)^2))

but I'm not sure if (or how) I should put this into an lm() or glm() in
order to get the coefficients out.

I'll summarize and post any replies. Thanks.

Cheryl G. Howard, D.Sc.
Senior Researcher
Thomson Labs
Rockville, MD

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