Displaying 2 results from an estimated 2 matches for "maxmass".
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mammals
2003 May 08
1
nls, restrict parameter values
...t hotmail.com>
>CC: <r-help at stat.math.ethz.ch>
>Subject: 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)....
2003 Apr 23
1
nls: Missing value or an Infinity produced when evaluating the model
...imization 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 evaluating the model
Is there anyway I can res...