[R] How to do a trig regression

[David Winsemius]

On Sep 12, 2010, at 10:23 PM, Aaditya Nanduri wrote:

> Hello All,
>
> I cant seem to do a trig regression in R.
>
> The equation is as follows : y = a+b*(sin((2*pi*x/360) - c))^2
>
> a, b, c are coefs that I want.
> y, x are input vectors.
>
> The equation I put into R: lm(y ~ sin(2*pi*x/360)^2)
> This equation is missing the c and I dont get the right answer.

Take a look at section 2.3 of:

http://www.statoek.wiso.uni-goettingen.de/veranstaltungen/zeitreihen/sommer03/ts_r_intro.pdf

Or consider using time series or nonlinear modeling.

> Also, I dont know how to plot the lm over the x values instead of the
> indices.

Without an example of your data and what you tried it is difficult to  
intuit what problems you may be facing.

-- 
David.
>
> Any help is sincerely appreciated.
> Thank you all very much.
>
> -- 
> Aaditya Nanduri
> aaditya.nanduri at gmail.com
>
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>
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