Displaying 2 results from an estimated 2 matches for "growthmodel".
2003 May 08
1
nls, restrict parameter values
...t: Re: [R] nls: Missing value or an Infinity produced when evaluating
>the model
>Date: Wed, 23 Apr 2003 15:22:37 +0200
>
>Hi Angel,
>
>I tried reparametrise your model, setting:
>
>BirthMass^0.25=u
>MaxMass^0.25=v
>
>and giving the following formula in R:
>
>GrowthModel<-nls(BodyMass~(((1-(1-u/v)*exp(-a*Time/(4*v)))^4)*v^4),data=grow
>th,start=c(u=4,v=5,a=1.5),trace=TRUE)
>
>And this works for me, but the u estimate is negative (not significantly
>different from 0, though).
>
>Christian
>
>----- Original Message -----
>From: "Ang...
2003 Apr 23
1
nls: Missing value or an Infinity produced when evaluating the model
...am getting
into some trouble.
Seems that the optimization method is getting down to some parameter
estimates that make the equation unsolvable. This is an example:
>growth<-data.frame(Time=c(5,7,9,11,13,15,17,19,21,23,25,27),BodyMass=c(45,85,125,210,300,485,570,700,830,940,1030,1120))
>GrowthModel<-nls(BodyMass~(((1-(1-((BirthMass/MaxMass)^0.25))*exp(-a*Time/(4*MaxMass^0.25)))^4)*MaxMass),data=growth,start=c(BirthMass=3,MaxMass=2500,a=1.5),trace=TRUE)
56043.86 : 3.0 2500.0 1.5
Error in numericDeriv(form[[3]], names(ind), env) :
Missing value or an Infinity produced when ev...