[R] Polynomial fitting

Gerrit Eichner Gerrit.Eichner at math.uni-giessen.de
Fri Jul 8 07:25:44 CEST 2011

Hello, mfa (Matti?),

if x and y contain the coordinates of your data points and k is the wanted 
polynomial degree, then

fit <- lm( y ~ poly( x, k))

fits orthonormal polynomials up to degree k to your data. Using

dummy.coef( fit)

should give the coefficients you are interested in.

  Hth  --  Gerrit

On Thu, 7 Jul 2011, mfa wrote:

> Hello,
> i'm fairly familiar with R and use it every now and then for math related
> tasks.
> I have a simple non polynomial function that i would like to approximate
> with a polynomial. I already looked into poly, but was unable to understand
> what to do with it. So my problem is this. I can generate virtually any
> number of datapoints and would like to find the coeffs a1, a2, ... up to a
> given degree for a polynomial a1x^1 + a2x^2 + ... that approximates my
> simple function. How can i do this with R?
> Your help will be highly appreciated!
> --
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Dr. Gerrit Eichner                   Mathematical Institute, Room 212
gerrit.eichner at math.uni-giessen.de   Justus-Liebig-University Giessen
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