[R] Global variables

[Sebastien Bihorel]

Thanks,

I will have a look at it.

Sebastien

Michael Bedward wrote:
> Hi Sebastian,
>
> You might also find the proto package useful as a way of restricting
> the scope of variables. It provides a more intuitive (at least to me)
> way of packaging variables and functions up into environments that can
> be related in a hierarchy.
>
> Michael
>
> On 10 January 2011 23:48, Sebastien Bihorel
> <Sebastien.Bihorel at cognigencorp.com> wrote:
>   
>> Thank Gabor and Duncan,
>>
>> That will be helpful.
>>
>> Gabor Grothendieck wrote:
>>     
>>> On Thu, Jan 6, 2011 at 4:59 PM, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:
>>>
>>>       
>>>> On 06/01/2011 4:45 PM, Sebastien Bihorel wrote:
>>>>
>>>>         
>>>>> Dear R-users,
>>>>>
>>>>> Is there a way I can prevent global variables to be visible within my
>>>>> functions?
>>>>>
>>>>>           
>>>> Yes, but you probably shouldn't.  You would do it by setting the environment
>>>> of the function to something that doesn't have the global environment as a
>>>> parent, or grandparent, etc.  The only common examples of that are baseenv()
>>>> and emptyenv().  For example,
>>>>
>>>> x <- 1
>>>> f <- function() print(x)
>>>>
>>>> Then f() will work, and print the 1.  But if I do
>>>>
>>>> environment(f) <- baseenv()
>>>>
>>>> then it won't work:
>>>>
>>>>
>>>>         
>>>>> f()
>>>>>
>>>>>           
>>>> Error in print(x) : object 'x' not found
>>>>
>>>> The problem with doing this is that it is not the way users expect functions
>>>> to work, and it will probably have weird side effects.  It is not the way
>>>> things work in packages (even packages with namespaces will eventually
>>>> search the global environment, the namespace just comes first).  There's no
>>>> simple way to do it and yet get access to functions in other packages
>>>> besides base without explicitly specifying them (e.g. you'd need to use
>>>> stats::lm(), not just lm(), etc.)
>>>>
>>>>
>>>>         
>>> A variation of this would be:
>>>
>>> environment(f) <- as.environment(2)
>>>
>>> which would skip over the global environment, .GlobEnv, but would
>>> still search the loaded packages.  In the example above x would not be
>>> found but it still could find lm, etc.
>>>
>>>
>>>
>>>       
>>        [[alternative HTML version deleted]]
>>
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