# Polynomial fitting

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## Polynomial fitting

 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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## Re: Polynomial fitting

 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! > > -- > View this message in context: http://r.789695.n4.nabble.com/Polynomial-fitting-tp3652816p3652816.html> Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html> and provide commented, minimal, self-contained, reproducible code. > --------------------------------------------------------------------- Dr. Gerrit Eichner                   Mathematical Institute, Room 212 [hidden email]   Justus-Liebig-University Giessen Tel: +49-(0)641-99-32104          Arndtstr. 2, 35392 Giessen, Germany Fax: +49-(0)641-99-32109        http://www.uni-giessen.de/cms/eichner______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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