[R] nls problem with R

Andrew Robinson A.Robinson at ms.unimelb.edu.au
Thu May 5 12:37:36 CEST 2011


Apologies, but I don't see a question here ... am I missing something
obvious?

Andrew

On Thu, May 05, 2011 at 01:20:33AM -0700, sterlesser wrote:
> ID1  ID2     t               V(t)
> 1	1	0	        6.053078443
> 2	1	0.3403	5.56937391
> 3	1	0.4181	5.45484486
> 4	1	0.4986	5.193124598
> 5	1	0.7451	4.31386722
> 6	1	1.0069	3.645422269
> 7	1	1.5535	3.587710965
> 8	1	1.8049	3.740362689
> 9	1	2.4979	3.699837726
> 10	1	6.4903	2.908485019
> 11	1	13.5049	1.888179494
> 12	1	27.5049	1.176091259
> 13	1	41.5049	1.176091259
> 
> The model
> (1)  V(t)=V0[1-epi+ epi*exp(-c(t-t0))]
> (2)  V(t)=V0{A*exp[-lambda1(t-t0)]+(1-A)*exp[-lambda2(t-t0)]}
> 
> in formula (2) lambda1=0.5*{(c+delta)+[(c-delta)^2+4*(1-epi)*c*delta]^0.5}
>                   
> lambda2=0.5*{(c+delta)-[(c-delta)^2+4*(1-epi)*c*delta]^0.5}
>                    A=(epi*c-lambda2)/(lambda1-lambda2)
> 
> The regression rule :
> for formula (1):(t<=2,that is) first 8 rows are used for non-linear
> regression
> epi,c,t0,V0 parameters are obtained 
> for formula (2):all 13 rows of results are used for non-linear regression 
> lambda1,lambda2,A (with these parameters, delta can be calculated from them)
> 
> Thanks for help
> Ster Lesser
> 
> --
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> 
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-- 
Andrew Robinson  
Program Manager, ACERA 
Department of Mathematics and Statistics            Tel: +61-3-8344-6410
University of Melbourne, VIC 3010 Australia               (prefer email)
http://www.ms.unimelb.edu.au/~andrewpr              Fax: +61-3-8344-4599
http://www.acera.unimelb.edu.au/

Forest Analytics with R (Springer, 2011) 
http://www.ms.unimelb.edu.au/FAwR/
Introduction to Scientific Programming and Simulation using R (CRC, 2009): 
http://www.ms.unimelb.edu.au/spuRs/



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