Dear Dr. Chandrasekhar, Writing code for that model looks like a non-trivial undertaking. Maybe someone else has more time to invest.
I would check to see if code was published with the 2009 paper. If not, I would recommend contacting the authors to ask for code. The paper would get more citations if they provide code. You can find general advice on fitting non-linear models in the following paper (let me know if you need a copy) Bolker, B. M., B. Gardner, M. Maunder, C. W. Berg, M. Brooks, L. Comita, E. Crone, S. Cubaynes, T. Davies, P. de Valpine, J. Ford, O. Gimenez, M. Kery, E. J. Kim, C. Lennert-Cody, A. Magnusson, S. Martell, J. Nash, A. Nielsen, J. Regetz, H. Skaug, and E. Zipkin. 2013. Strategies for fitting nonlinear ecological models in R, AD Model Builder, and BUGS. Methods in Ecology and Evolution:1–12. Cheers, Mollie ------------------------ Mollie Brooks, PhD Postdoctoral Researcher, Population Ecology Research Group Institute of Evolutionary Biology & Environmental Studies, University of Zürich http://www.popecol.org/team/mollie-brooks/ > On 6Dec 2014, at 6:22, Chandrasekhar Rudrappa <chandr...@gmail.com> wrote: > > Dear All, > > > I have to fit the following model to growth data of Hevea (rubber) trees: > > *a=a-(a-b)exp(-(2/p)(F(t)-F(t0))).* Where *F(t)=t+(A/2pi)(sin 2pi(t-t1))*, > > *F(t0)=t0+(A/2pi)(sin 2pi(t0-t1)), t1* signifies the maximum point of > *f(t)*. Thus the equation becomes: > > *a=a-(a-b)exp(-(2/p)(t+(A/2pi)(sin 2pi(t-t1)))- (t0+(A/2pi)(sin > 2pi(t0-t1))))* > > Up to this step, I have succeeded very well. > > > > *My problem is with the following model for which I need help. * > > > > The same equation is further developed into a seasonal cessation model by > deriving equivalent equations to replace *F(t)*. For the purpose of > seasonal cessation model *F(t)* is derived as: > > > > * n(1-T)+S(t-n) (n<=t<n+t2), * > > *F(t) = n(1-T)+S(t2) (n+t2<=t<n+t3), * > > * n(1-T)+S(t-n-T) (n+t3<=t<n+1),* > > > > where *S(t)=t+((1-T)/(2pi))(sin 2pi((t-t1)/(1-T))),* n=integral part of t, > > > > *t2=t1+(1-T)/2, t3=t1+(1+T)/2 , T=no growth period. *Similarly the above > equations have to be modified *for F(to).* These have to be integrated in > to: > > > > *a=a-(a-b)exp(-(2/p)(F(t)-F(t0))).* > > > > Kindly help with a suitable code to fit the above model to my data. > > > > References: 1. Akamine, T (1993). A New Standard Formula for Seasonal > Growth of Fish in Population Dynamics. Nippon Suisan Gakkaishi > 59(11):1857-1863. > > 2. Akamine, T (2009). Non-linear and graphical methods for fish stock > analysis with statistical modelling. Aqua-BioScience Monographs VOL. 2 NO. 3 > :1-45. > > > -- > Dr. TR Chandrasekhar, M.Sc., M. Tech., Ph. D., > Sr. Scientist > Rubber Research Institute of India > Hevea Breeding Sub Station > Kadaba - 574 221 > DK Dt., Karnataka > Phone-Land: 08251-214336 > Mobile: 9448780118 > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-ecology mailing list > R-sig-ecology@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > [[alternative HTML version deleted]] _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology