[R] reporting multiple objects out of a function

[Paul Hiemstra]

On 10/05/2011 04:27 AM, andrewH wrote:
> Dear folks, 
>
> I’m trying to build a function to create and make available some variables I
> frequently use for testing purposes.  Suppose I have a function that takes
> some inputs and creates (internally) several named objects. Say, 
>
> fun1 <- function(x, y, z) {obj1 <- x; obj2 <- y; obj3 <- z
> <missing stuff>
> }
>
> Here is the challenge: After I run it, I want the objects to be available in
> the calling environment, but not necessarily in the global environment.  I
> want them to be individually available, not as part of a list or some larger
> object.  I can not figure out how to do this.  If I understand the situation
> correctly, I am trying to move several separate objects from the environment
> of the function to the environment in which the function was invoked (the
> “calling environment,” yes?).  
>
> I’m pretty sure there is a command to do this, but I’m not sure how to find
> it. Any help would be greatly appreciated – either on the necessary code, or
> on how to search for it, or a reference to a good discussion of this family
> of problems.
>
> Sincerely, andrewH
>
>
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Hi,

You can use the <<- operator. Although in the spirit of fortune(106),
"If <<- is the answer, rethink your question...". Why is it important
that your objects are not part of a larger object, which is standard
practice in R. You could also take a look at the attach() command:

bla = fun1(x,y,z)
attach(bla)

Note that in fun1 you do need to return your objects in a list. However,
I'm still not in favor of using this approach...

good luck,
Paul

-- 
Paul Hiemstra, Ph.D.
Global Climate Division
Royal Netherlands Meteorological Institute (KNMI)
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