[R] Polynomial equation

[chrisli1223]

Thank you very much for your help. Greatly appreciated!

However, due to my limited stats background, I am unable to find out the
equation of the trendline from the summary table. Besides, how do I fit the
trendline on the graph?

I intend to put the first column of data onto x axis and the second column
onto y axis. Are they the x and y in your example?

Many thanks,
Chris


Moshe Olshansky-2 wrote:
> 
> 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
>> -- 
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>> http://n4.nabble.com/Polynomial-equation-tp1009398p1009398.html
>> Sent from the R help mailing list archive at Nabble.com.
>> 
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> 
> ______________________________________________
> 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.
> 
> 

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