R help - May 2012 - Problems accessing environment() in function

Hi all,

I am trying to create a list of all variable/value combinations in 
environment().

When a function with unset arguments is called, the method I have been 
using fails with a "missing argument" error. However it should be 
possible to simply skip these missing objects in the generation of the list?

Could anyone recommend me a better way (that does not use a slow 
for/eval-combination) to achieve the desired effect?

You can easily reproduce my problem using this code:

------------------------------

test1 <- function(a, b, c)
{
   x <- as.list(environment())
   print ("hi from test1!")
   test2(a = a, b = b, c = c)
}

test2 <- function(a, b, c)
{
   # PROBLEM: Why can't I get a list as in test1() here?
   x <- as.list(environment())
   print ("hi from test2!")
}

test1()

------------------------------

I want my list "x" in test2() to work behave just like "x"
in test1().
(In this example the correct list in test2() would be empty).

Thanks a lot for your time.

Best wishes,
Heiko Neuhaus

On 01.05.2012 19:57, Heiko Neuhaus wrote:
> Hi all,
>
> I am trying to create a list of all variable/value combinations in
> environment().
>
> When a function with unset arguments is called, the method I have been
> using fails with a "missing argument" error. However it should be
> possible to simply skip these missing objects in the generation of the
> list?
>
> Could anyone recommend me a better way (that does not use a slow
> for/eval-combination) to achieve the desired effect?
>
> You can easily reproduce my problem using this code:
>
> ------------------------------
>
> test1 <- function(a, b, c)
> {
> x <- as.list(environment())
> print ("hi from test1!")
> test2(a = a, b = b, c = c)
You are rying to pass a, b, c here and hence R tries to insert those 
into the environment of test2 once it is called, you have not passed 
arguments to your test1 call.

Uwe Ligges
> }
>
> test2 <- function(a, b, c)
> {
> # PROBLEM: Why can't I get a list as in test1() here?
> x <- as.list(environment())
> print ("hi from test2!")
> }
>
> test1()
>
> ------------------------------
>
> I want my list "x" in test2() to work behave just like
"x" in test1().
> (In this example the correct list in test2() would be empty).
>
> Thanks a lot for your time.
>
> Best wishes,
> Heiko Neuhaus
>
> ______________________________________________
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> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Thanks a lot for your answer!
>> ------------------------------
>>
>> test1 <- function(a, b, c)
>> {
>> x <- as.list(environment())
>> print ("hi from test1!")
>> test2(a = a, b = b, c = c)
>
> You are rying to pass a, b, c here and hence R tries to insert those
> into the environment of test2 once it is called, you have not passed
> arguments to your test1 call.
>
> Uwe Ligges
I am aware that I am passing non existing arguments here, which is why 
my method of creating a list of the environment
"as.list(environment())"
seems to fail in this case.

What I need is a way to just skip non existing objects when I create my 
list. In my given example I was intending to receive an empty list, 
since no valid arguments were passed to test2().

In other words: I want a list containing all _existing_ variable/value 
combinations and just skip the missing ones.

Thanks again for your time

Best wishes,
Heiko Neuhaus