[Rd] Defining environments within functions

[Duncan Murdoch]

Matt Calder wrote:
> Duncan,
>
>     Sorry to be, well, nit picking, but I can't get your example to run. I 
> am a longtime Splus user and am only using R on the side. The concept of 
> environments is one I have yet to grasp. I think the example you are trying 
> to provide will illuminate things for me, but it doesn't source. The 
> definition of fnBuilder sources fine, though I am not sure what the 
> "commonArgs <- ..." is meant to do. Anyway, calling:
>   

That wasn't R code, it was pseudocode.  That's why I asked the original 
poster for a real example: pseudocode examples aren't useful.  But I 
shouldn't have posted one myself, I should just have stopped at the 
first paragraph.

Duncan Murdoch
>   
>> both <- fnBuilder(...)
>>     
> Error: '...' used in an incorrect context
>
> and so I though, maybe you meant:
>
>   
>> both <- fnBuilder(c(1,2,3))
>>     
> Error in fnBuilder(c(1, 2, 3)) : '...' used in an incorrect context
>
> But then I thought you were perhaps using "..." as a placeholder not as 
> syntax and so I have little idea what it is you are trying to show. Could 
> you clarify what your example is demonstrating in regards to scoping?
>
>     So far, I have found the only part of R my Splus knowledge doesn't 
> translate is in regard to this sort of thing. I can't tell you how much pain 
> translating "substitute" idioms into R has caused me. Thanks,
>
>     Matt
>
>
>
>
> ----- Original Message ----- 
> From: "Duncan Murdoch" <murdoch at stats.uwo.ca>
> To: <gjh27 at cornell.edu>
> Cc: <r-devel at r-project.org>
> Sent: Thursday, August 28, 2008 5:42 AM
> Subject: Re: [Rd] Defining environments within functions
>
>
>   
>> Giles Hooker wrote:
>>     
>>> How can I define environments within a function so that they are visible
>>> to calls to a sub-function?
>>>
>>>       
>> I think you need to give a simplified, runnable example.  (Or at least 
>> runnable until it hits the scoping problem you've got.)  "Sub-function" 
>> isn't R terminology, and it's not clear what you mean by it.
>>
>> In R, you rarely need to work with environments explicitly.  You just 
>> define functions in the same location and they share the same environment. 
>> For example,
>>
>> fnBuilder <- function(commonArgs) {
>>  commonVars <- ...
>>  ProfileErr <- function(params, ...) {}
>>  coefs <- function(params, ...) {}
>>  return(list(ProfileErr, coefs))
>> }
>>
>> both <- fnBuilder(...)
>> ProfileErr <- both[[1]]
>> coefs <- both[[2]]
>>
>> Now ProfileErr and coefs share the same environment, and both can see (and 
>> modify) commonArgs and commonVars.
>>
>> Duncan Murdoch
>>
>>
>>     
>>> I have defined an objective function,
>>>
>>> ProfileErr = function(params,...)
>>>
>>> which I would like to optimize using standard routines (optim,
>>> nlminb,....) but which contains auxiliary variables which need to be
>>> updated along with params. No optimization routine in R that I have
>>> found has facilities for this.
>>>
>>> Specifically, within ProfileErr, I need to calculate
>>>
>>>   coefs(params,...)
>>>
>>> This a function which requires a further optimization, and I can achieve
>>> significant efficiency gains by starting  where the last optimization
>>> ended, so I would like to keep track of it.
>>>
>>> At the command line, I get around this by
>>>
>>> ProfileEnv = new.env()
>>> assign('coefs',coefs,3,ProfileEnv)
>>>
>>> and within ProfileErr, I can call
>>>
>>> startcoefs = get('coefs',envir=ProfileEnv)
>>> * do the optimization to get newcoefs *
>>> assign('coefs',newcoefs,3,ProfileEnv)
>>>
>>> Then calling
>>>
>>> optim(pars,ProfileErr,....)
>>>
>>> works fine. However, when I try to wrap all of that in its own function
>>>
>>> profile.estimate = fn(pars,...){
>>> ProfileEnv = new.env()
>>> assign('coefs',coefs,3,ProfileEnv)
>>>
>>> res = optim(pars,ProfileErr,....)
>>> }
>>>
>>>
>>> ProfileErr no longer sees ProfileEnv. I haven't been able to make much
>>> sense out of the documentation on environments, but is there a way to
>>> make this work? Otherwise I'm back to writing variables out to files.
>>>
>>> Many thanks,
>>>
>>> Giles
>>>
>>>
>>>
>>>       
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>>
>>     
>
>