In addition to the other comments, you may find it helpful to look at "using function derivative information" in the nonlinear regression section of Venables and Ripley. David
[EMAIL PROTECTED] wrote on 10/29/2008 07:56:01 AM: > Dear R-ecology subscribers, > > > > Here is a small contamination data set: ââ¬Ëchlordââ¬â¢ extracted from > a publication (Bahner and Oglesby USEPA): > > V1 V2 > > 1 0 0.000000 > > 2 7 1.579784 > > 3 9 1.857332 > > 4 14 1.944483 > > 5 21 2.079181 > > 6 28 1.939519 > > 7 30 2.000000 > > 8 35 2.000000 > > 9 42 1.924279 > > 10 49 1.740363 > > 11 56 1.361728 > > > > I would like to translate this old SAS script (provided), to actual R code : > > PROC SORT; BY SPECIES CONC TISSUE; > > PROC NLIN BEST = 0.5 ITER = 200 METHOD = MARQUARDT; BY > > SPECIES CONC TISSUE; > > PARMS A = 0.1 TO 0.3 by 0.1 > > C = 0.1 TO 0.7 by 0.2 > > D = âââ¬0.1 TO 0.3 by 0.2; > > Q = (A + 10**(âââ¬C*DAY))); E = 28; > > R = (A + 10**EXP(âââ¬D*(DAYâââ¬E))); > > MODEL Y = Q**(âââ¬1) ââ⬠R**(âââ¬1); > > DER.A = ââ⬠(Q** (âââ¬2)) + R** (âââ¬1); > > DER.C = (Q** (âââ¬2))* (10** (âââ¬C*DAY))*DAY*LOG(10); > > DER.D = âââ¬10* (DAY ââ⬠E)*EXP (âââ¬D*(DAY ââ⬠> E))*R**(âââ¬2); > > _____WEIGHT____ = DAY; > > > > I tried the nls function: > > fm<-nls(V2~(A+(10^(-C*V1)))^-1-(A+10^exp(-D*(V1-28)))^-1, > data=chlord, trace=TRUE, start=c(A=0.1,C=0.1,D=-0.1), nls.control > (maxiter = 200)) > > with an extensive research through web, but found no information > about how to take into account the DER.A, DER.C and DER.D in R code, > for optimization. > > > > thank you in advance for any information > > Dominique > > > > ______________________________ > > D. Monti > > Marine Lab. > > University of Antilles and Guyane > > Little Island of Guadeloupe, FWI > > > > > > [[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