[R] nls and R scoping rules

[joerg van den hoff]

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.

joerg