[R] Return a list

[Wacek Kusnierczyk]

that's likely to work, but it's even worse than my non-functional
version: the destructive operation on the test's caller's environment is
performed here by the callee (test), and you can get ugly surprises if
you forget that test does that. 

i'd consider this (and the 'for (name in names(result)) assign(...)'
solution) an anti-pattern. 


vQ

N. Lapidus wrote:
> The answers that were previously given allow you to easily extract results
> from your returned list, but if I understand well, this list is created only
> because you cannot return several arguments whereas you need to keep the
> values of a, b, c, etc. Am I right?
> Another solution would be to directly "send" the values you want to keep
> into the environment where they are needed. The following example supposes
> you need to keep "a" only in the upper environment from which your function
> was launched, and "b" in another one (e.g. .GlobalEnv).
> Hope this may help.
> Nael
>
>   
>> # Here is a function such as yours:
>> test <- function(){
>>     
> + a <- 1
> + b <- 2
> + return(list(a=a, b=b, c=c))
> + }
>   
>> result <- test()
>> (a <- result$a)
>>     
> [1] 1
>   
>> (b <- result$b)
>>     
> [1] 2
>   
>> rm(a, b)
>>
>> # Now our variables will be automatically assigned into the chosen
>>     
> environment
>   
>> test2 <- function(){
>>     
> + a <- 1
> + b <- 2
> + assign("a", a, envir=parent.frame(n=1))
> + assign("b", b, envir=.GlobalEnv)
> + return(NULL)
> + }
>   
>> # Suppose test2 is launched by another function
>> test2.launcher <- function() {
>>     
> + test2()
> + print(paste("a exists inside test2.launcher:", exists("a")))
> + print(paste("b exists inside test2.launcher:", exists("b")))
> + return (NULL)
> + }
>
>   
>> test2.launcher()
>>     
> [1] "a exists inside test2.launcher: TRUE"
> [1] "b exists inside test2.launcher: TRUE"
> NULL
>   
>> exists("a")# a still exists in the upper environment
>>     
> [1] FALSE
>   
>> exists("b")# b does not
>>     
> [1] TRUE
>
>
>
>