R help - Jan 2012 - How to define a variable in a function that another function uses without using global variables

I would like to know if it is possible to make a function that defines a
variable in another function without setting that variable globally?

I would i.e. be able to define a variables value inside a function ("one
level above) which another function makes use of, without setting this
variable globally.

I have provided this very simple illustrating example.

test1=function(x)
	{
	x+y
	}
test2=function(y1)
	{
	y=y1
	test1(2,y1)
	}

Running the second function results in an error:
> test2(1)
Error in test1(2) : object 'y' not found

I see 2 possible solutions to this, but neither of them is preferred in my
more complex situation:

1. Setting y<<-y_1 globally in test2-function
2. making test1 a function of both x and y.

Is there any other way to do this except from the 2 above? I hope someone
can help me with this.

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Consider this example:

power <- function(n){
    function(x) x^n
} # Note that this function returns a function!

cube <- power(3)

cube(2) # gives 8

That make sense?

Michael

On Wed, Jan 18, 2012 at 1:30 PM, statguy <martinju at mail.com>
wrote:
> I would like to know if it is possible to make a function that defines a
> variable in another function without setting that variable globally?
>
> I would i.e. be able to define a variables value inside a function
("one
> level above) which another function makes use of, without setting this
> variable globally.
>
> I have provided this very simple illustrating example.
>
> test1=function(x)
> ? ? ? ?{
> ? ? ? ?x+y
> ? ? ? ?}
> test2=function(y1)
> ? ? ? ?{
> ? ? ? ?y=y1
> ? ? ? ?test1(2,y1)
> ? ? ? ?}
>
> Running the second function results in an error:
>> test2(1)
> Error in test1(2) : object 'y' not found
>
> I see 2 possible solutions to this, but neither of them is preferred in my
> more complex situation:
>
> 1. Setting y<<-y_1 globally in test2-function
> 2. making test1 a function of both x and y.
>
> Is there any other way to do this except from the 2 above? I hope someone
> can help me with this.
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/How-to-define-a-variable-in-a-function-that-another-function-uses-without-using-global-variables-tp4307604p4307604.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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.

Make an environment that the functions share.  One way to do
this is with local():
> test <- local({ y <- NA
+                 f1 <- function(x) x + y
+                 f2 <- function(y1) { y <<- y1 ; f1(1) }
+                 list(f1=f1, f2=f2) })
> test$f2(2^(1:3))
[1] 3 5 9  

(The example you showed must have had a typo in it,
as it didn't give the error message you showed.  I
assume you typed 'test1(2,y1)' where you meant 'test1(2)'.)

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org] On Behalf Of statguy
> Sent: Wednesday, January 18, 2012 10:30 AM
> To: r-help at r-project.org
> Subject: [R] How to define a variable in a function that another function
uses without using global
> variables
> 
> I would like to know if it is possible to make a function that defines a
> variable in another function without setting that variable globally?
> 
> I would i.e. be able to define a variables value inside a function
("one
> level above) which another function makes use of, without setting this
> variable globally.
> 
> I have provided this very simple illustrating example.
> 
> test1=function(x)
> 	{
> 	x+y
> 	}
> test2=function(y1)
> 	{
> 	y=y1
> 	test1(2,y1)
> 	}
> 
> Running the second function results in an error:
> > test2(1)
> Error in test1(2) : object 'y' not found
> 
> I see 2 possible solutions to this, but neither of them is preferred in my
> more complex situation:
> 
> 1. Setting y<<-y_1 globally in test2-function
> 2. making test1 a function of both x and y.
> 
> Is there any other way to do this except from the 2 above? I hope someone
> can help me with this.
> 
> --
> View this message in context:
http://r.789695.n4.nabble.com/How-to-define-a-variable-in-a-function-
>
that-another-function-uses-without-using-global-variables-tp4307604p4307604.html
> Sent from the R help mailing list archive at Nabble.com.
> 
> ______________________________________________
> R-help at r-project.org mailing list
> 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.

Great! 
That works perfectly sense. Thanks a lot!

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