[R] Truly Global Variables

[Duncan Murdoch]

On 11-01-22 3:06 AM, Lui ## wrote:
> Hello everybody,
>
> I have a problem that is bothering me for  quite a while now and I
> don't know the answer... I want to create global variables (out of a
> function) which I can access from all other functions... But somehow
> that does not work too well. Attached some code for an example:
>
> function_called<- function (){
> 	result = globalvariable*globalvariable
> 	print(result)
> 	
> 	}
>
> function_calls<- function(){
> 	assign("globalvariable",10,pos=-1,envir=as.environment(pos))

This line doesn't make sense.  Why specify both pos and envir?  I would 
have used envir=globalenv() to do what you want; the help page indicates 
that pos=globalenv() is preferred by whoever wrote it.  But don't use both.

However, an even simpler approach is simply

globalvariable <<- 10

This will search back through the environments associated with the 
function_calls function (not the call stack!) for a variable named 
globalvariable, and make the assignment to it.  If none exists, it will 
use the global environment.

Duncan Murdoch

> 	function_called()
> 	}
>
> function_calls()
>
> I would have assumed that I will get "100" printed on my screen, but
> instead it said: "Fehler in function_called() : Objekt
> 'globalvariable' nicht gefunden", so the function "function_called"
> did not have access to the variable "globalvariable".
>
> I would be very thankful for some help... I want to implement it in
> the genetic algorithms provided by the rgenoud package and dont know
> any other way to have "changing" constraints (e.g. Portfolio
> optimization and covariance matrix).
> Thanks in advance! Any help greatly appreciated!
>
> Lui
>
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