Thank you all for your help.
Felipe D. Carrillo Supervisory Fishery Biologist Department of the Interior US Fish & Wildlife Service California, USA http://www.fws.gov/redbluff/rbdd_jsmp.aspx >________________________________ >From: Gabor Grothendieck <ggrothendi...@gmail.com> >To: Felipe Carrillo <mazatlanmex...@yahoo.com> >Cc: "r-help@r-project.org" <r-help@r-project.org> >Sent: Thursday, July 12, 2012 1:03 PM >Subject: Re: [R] nls question > >On Thu, Jul 12, 2012 at 3:40 PM, Felipe Carrillo ><mazatlanmex...@yahoo.com> wrote: >> I get a different error now: >>> nls(weight ~ cbind(1, exp(gamma*week)), weightData, start = list(gamma= >>> 0.2), alg = "plinear") >> Error in nls(weight ~ cbind(1, exp(gamma * week)), weightData, start = >> list(gamma = 0.2), : >> step factor 0.000488281 reduced below 'minFactor' of 0.000976562 >> The help file says: ........When start is missing, a very cheap guess for >> start is tried (if algorithm != "plinear"). > > >Please give a reproducible example by setting the seed. This >reproducible example converges: > >> set.seed(123) >> weight_random <- runif(50,1,24) >> weight <- sort(weight_random) >> weightData <- data.frame(weight,week=1:50) >> nls(weight ~ cbind(1, exp(gamma*week)), weightData, start = list(gamma = >> 0.2), alg = "plinear") >Nonlinear regression model > model: weight ~ cbind(1, exp(gamma * week)) > data: weightData > gamma .lin1 .lin2 >1.136e-03 -3.949e+02 3.962e+02 >residual sum-of-squares: 9.17 > >Number of iterations to convergence: 8 >Achieved convergence tolerance: 9.581e-06 > >as does nls with Gauss Newton: > >> nls(weight ~ alpha + beta*exp(gamma*week), weightData, start = >+ c(alpha = 0.0, beta = 1, gamma = 0.2) >+ ) >Nonlinear regression model > model: weight ~ alpha + beta * exp(gamma * week) > data: weightData > alpha beta gamma >-3.949e+02 3.961e+02 1.136e-03 >residual sum-of-squares: 9.17 > >Number of iterations to convergence: 48 >Achieved convergence tolerance: 2.906e-06 > >> >> So I removed 'plinear' from the call and got the following: >> nls(weight ~ cbind(1, exp(gamma*week)), weightData,start = >> list(gamma=0.2),trace=TRUE) > >It cannot be specified as if it were a plinear model but then use >Gauss-Newton. See ?nls > > >-- >Statistics & Software Consulting >GKX Group, GKX Associates Inc. >tel: 1-877-GKX-GROUP >email: ggrothendieck at gmail.com > > > [[alternative HTML version deleted]]
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