# Re: [R] fitting periodic 'sine wave' model

From: Søren Højsgaard <Soren.Hojsgaard_at_agrsci.dk>
Date: Tue, 10 Jun 2008 22:21:28 +0200

If you make the x-values more dense, e.g. with x<-seq(0,20,0.1) then your example works. Plotting your data might give a hint to why your example fails.... Btw: It is generally not a good idea to use F for a parameter because F usually means FALSE. Regards
Søren

Fra: r-help-bounces_at_r-project.org på vegne af Jon Loehrke Sendt: ti 10-06-2008 16:25
Til: r-help_at_r-project.org
Emne: [R] fitting periodic 'sine wave' model

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

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