Using varPower in gnls, an answer of sorts.
On Wed, 2 Mar 2005 Setzer.Woodrow at epamail.epa.gov wrote:
Back on January 16, a message on R-help from Ravi Varadhan described a problem with gnls using weights=varPower(). The problem was that the fit failed with error
[...]
I'm sending this to r-help rather to the authors of nlme because I am not sure where the bug is: is model.frame misbehaving, or should gnls not include '.' in its call to model.frame?
'.' is only defined in a formula for model.frame() when there is a 'data' argument (otherwise what do you think it might mean?). So this is not a problem in model.frame(), hence on your analysis in gnls() or the usage of it.
Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595