# [R] fitting periodic 'sine wave' model

Søren Højsgaard Soren.Hojsgaard at agrsci.dk
Tue Jun 10 22:21:28 CEST 2008

```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

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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
Department of Fisheries Oceanography
School for Marine Science and Technology
University of Massachusetts
Fairhaven, MA 02719
jloehrke at umassd.edu
T 508-910-6393
F 509-910-6396

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