R help - Nov 2009 - regression with a*cos(angle+phi)+b

Hello,

the only thing I found to fit a sin/cos is s.th like lm(a~cos+sin) But
this is not what I want.
I have a magnitude which is sinusoidal with offset and it doesn't start
at phi=0.

The data is:

angle<-c(0,10,20,30,40,50,60,70,80,90,100,110,120,130,140,150,160,170,180)

Voltage<-c(-45.07, -45.24, -43.61, -40.78, -36.48, -30.92, -23.83,
-15.95,  -7.53,   1.06,  11.24,19.85,  27.00,  35.00,  42.90,  49.41,
54.62,  58.54,  60.90)

I need an regression with Voltage=A*cos(angle+phi)+B.
How does this work? With lm or shall I use twice Fourier?

thanks

Markus

Good morning Markus,

Perhaps ?nls might be useful in this case.

HTH,
Jorge


On Mon, Nov 30, 2009 at 7:19 AM, Markus Häge <> wrote:
> Hello,
>
> the only thing I found to fit a sin/cos is s.th like lm(a~cos+sin) But
> this is not what I want.
> I have a magnitude which is sinusoidal with offset and it doesn't start
> at phi=0.
>
> The data is:
>
>
angle<-c(0,10,20,30,40,50,60,70,80,90,100,110,120,130,140,150,160,170,180)
>
> Voltage<-c(-45.07, -45.24, -43.61, -40.78, -36.48, -30.92, -23.83,
> -15.95,  -7.53,   1.06,  11.24,19.85,  27.00,  35.00,  42.90,  49.41,
> 54.62,  58.54,  60.90)
>
> I need an regression with Voltage=A*cos(angle+phi)+B.
> How does this work? With lm or shall I use twice Fourier?
>
> thanks
>
> Markus
>
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