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