[R] fitting periodic 'sine wave' model

[Jon Loehrke]

I have been attempting to estimate the periodic contribution of an  
effect to some data but have not been able to fit a sine wave within R.
It would be nice to start by being able to fit a sine wave with an  
amplitude and frequency.

x<-seq(0,20,by=0.5)
y<-2*sin(2*pi*.5*x) #amplitude =2, frequency=0.5

# This failed to converge
r<-nls(y ~ A*sin(2*pi*F*x), start=list(A = 1, F = 1), trace=T)


# even this gave a max iteration error
r<-nls(y ~ A*sin(2*pi*F*x), start=list(A = 1, F = .5), trace=T)

I have a feeling I am approaching this incorrectly.  Thank you all  
very much for the guidance.

Jon
R 2.7.0
mac os 10.5


Jon Loehrke
Graduate Research Assistant
Department of Fisheries Oceanography
School for Marine Science and Technology
University of Massachusetts
200 Mill Road, Suite 325
Fairhaven, MA 02719
jloehrke at umassd.edu
T 508-910-6393
F 509-910-6396