Hi Chris, You can use lm with poly (look ?lm, ?poly). If x and y are your arrays of points and you wish to fit a polynom of degree 4, say, enter: model <- lm(y~poly(x,4,raw=TRUE) and then summary(model) The raw=TRUE causes poly to use 1,x,x^2,x^3,... instead of orthogonal polynomials (which are "better" numerically but may be not what you need).
Regards, Moshe. --- On Fri, 8/1/10, chrisli1223 <chri...@austwaterenv.com.au> wrote: > From: chrisli1223 <chri...@austwaterenv.com.au> > Subject: [R] Polynomial equation > To: r-help@r-project.org > Received: Friday, 8 January, 2010, 12:32 PM > > Hi all, > > I have got a dataset. In Excel, I can fit a polynomial > trend line > beautifully. However, the equation that Excel calculates > appear to be > incorrect. So I am thinking about using R. > > My questions are: > (1) How do I fit a polynomial trendline to a graph? > (2) How do I calculate and display the equation for that > trendline? > > Many thanks for your help. Greatly appreciated. > > Chris > -- > View this message in context: > http://n4.nabble.com/Polynomial-equation-tp1009398p1009398.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org > 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. > ______________________________________________ R-help@r-project.org 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.
