Message-ID: <1204878694.26892.6.camel@localhost.localdomain>
Date: 2008-03-07T08:31:34Z
From: Firas Swidan
Subject: Puzzling coefficients for linear fitting to polynom
Hi,
I can not comprehend the linear fitting results of polynoms. For
example, given the following data (representing y = x^2):
> x <- 1:3
> y <- c(1, 4, 9)
performing a linear fit
> f <- lm(y ~ poly(x, 2))
gives weird coefficients:
> coefficients(f)
(Intercept) poly(x, 2)1 poly(x, 2)2
4.6666667 5.6568542 0.8164966
However the fitted() result makes sense:
> fitted(f)
1 2 3
1 4 9
This is very confusing. How should one understand the result of
coefficients()?
Thanks for any tips,
Firas.
--
Firas Swidan, PhD
Founder and CEO
Olymons: Blessing Machines with Vision (TM)
http://www.olymons.com
P.O.Box 8125
Nazareth 16480
Israel
Cell: +.972.(0)54.733.1788