Juan Manuel Barreneche wrote: > i guess nls or gnls should work.... > Yes. Notice though that this is really a linear problem because of the trigonometric identity
sin(x+b) = cos(b) * sin(x) + sin(b) * cos(x) which means that you can reparametrize c*sin(x+b) (you forgot the multiplier, did you not?) as A*sin(x)+B*cos(x) It is easy to invert the reparametrization if you notice that A^2 + B^2 = c^2, but it may be expedient to use the nonlinear functions to get confidence itervals for a,b,c. > JM > > El Viernes, 23 de Mayo de 2008 10:47, Zroutik Zroutik escribió: > >> Dear R-users, >> >> I'd like to fit a sine function to my data. The result should have a format >> (and thus the formula, too) >> >> y ~ a + sin(x+b) >> >> where y and x are vectors, and a and b are (yet) unknown values. >> >> The data sets (vectors x and y) are OK, and I can do a simple lm fitting >> lm(y~x), or lm(y~I(sin(2*pi*x/360))), succesfully My issue is that I'm not >> able to do the optional linear shift in x (e.g. x+b). What other >> possibilities should I use instead of lm? I looked searched the R-seek for >> terms: fit, sine, lm, and combinations, but I could not find anything >> useful. Anybody would be so kind and point me to the right direction where >> I can find other fitting possibilities? >> >> Thank you for listening and kind answers upfront. >> >> Regards, >> Milan >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html and provide commented, minimal, >> self-contained, reproducible code. >> > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
