[R] Polynomial equation

[Moshe Olshansky]

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 <chrisli at austwaterenv.com.au> wrote:

> From: chrisli1223 <chrisli at austwaterenv.com.au>
> Subject: [R]  Polynomial equation
> To: r-help at 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 at 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.
>