[R] nls and R scoping rules

[Prof Brian Ripley]

On Thu, 10 Jun 2004, joerg van den hoff wrote:

> Prof Brian Ripley wrote:
> 
> >On Thu, 10 Jun 2004, Prof Brian Ripley wrote:
> >
> >  
> >
> >>Around R 1.2.x the notion was introduced that variables should be looked 
> >>for in the environment of a formula.  Functions using model.frame got 
> >>converted to do that, but nls did not.  I guess that the best way forward 
> >>is to ensure that nls (and nlsModel) does search the environment of the 
> >>formula for functions.
> >>    
> >>
> >
> >It transpires that is rather easy to achieve.  At the top of nlsModel and 
> >nlsModel.plinear use
> >
> >    env <- new.env(parent=environment(form))
> >
> >instead of
> >
> >    env <- new.env()
> >
> >This then automatically searches for objects used in the formula
> >
> >Notes
> >
> >1) nls is in a namespace, so you need to fix the copy in the namespace or 
> >fix the source code and rebuild.
> >
> >2) This will add to the baggage needed when you save() a nls fit in a 
> >workspace.  I think that is inevitable as we cannot just identify the 
> >funtions used in the formula (as they might call other functions in the 
> >local environment), and it is necessary to capture the objects needed to 
> >evaluate the formula for the predict() method to be reliable.
> >
> >We could call all.names() to get the names of functions used directly in 
> >the formula, but that seems not good enough (previous para).
> >
> >Question to the cognescenti: is the price in 2) too great for this to be 
> >done for 1.9.1?  I will put the change in R-devel for now.
> >
> >  
> >
> thank's a lot for the two responses. that  seems exactly what helps me out.
> 
> remaining question: how can I edit (I mean from within R, not by messing 
> around with the source code directly) an invisible function object such 
> as "nlsModel.plinear"?
> help.search('invisible'), help('function'), help('edit') at least did 
> not tell me.

It depends why they are hidden, but for functions not exported from a
namespace see ?fixInNamespace (hence my comment about namespaces).

-- 
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