# [R] Polynomial equation

chrisli1223 chrisli at austwaterenv.com.au
Fri Jan 8 04:14:27 CET 2010

```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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>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
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>> reproducible code.
>>
>
> ______________________________________________
> 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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