[R] nlsList{nlme} control of min and max parameter bounds?

[Dieter Menne]

Steve Oswald wrote:
> 
> I'm analysing growth rates using a gompertz (logistic) curve and am
> attempting
> to fit parameters for all of my study birds using nlsList.
> 
> I've been looking for an option in nlsList to set min and max limits for
> parameter values during estimation, although I have failed to find any
> under
> 'control'. 
> 

If you want to constrain to positive parameters only, as in pharmacology,
fitting the logs of the parameters might help. For more general constraints,
check the examples in optim.

Dieter





Hi All


I'm analysing growth rates using a gompertz (logistic) curve and am
attempting
to fit parameters for all of my study birds using nlsList.


I've been looking for an option in nlsList to set min and max limits for
parameter values during estimation, although I have failed to find any under
'control'. Other users seem to have reported that using control in the port
algorithm (as in an nls fit) failed to work and it didn't work in my case
either. Is there such a control for nlsList?


I did fashion a selfStart function with a work-around loop in it. This
subsetted the data by ID and performed separate nls fits with parameters
constrained by the port algorithm. My objective was to use nlsList as an
object
for an nlme fit, so I was thinking of pasting together the details of the
fits
from my slefStart function into an object of class "nlsList" "lmList" but
wasn't sure if this would work or was even appropriate.


Thanks for your help


Steve


Dr. Steve Oswald


Penn State Berks

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