As a followup to my question yesterday, what if I were to return the
argument as a list, and then "unwrap" the list with the function I've
written called "objects". Is there any problems with doing it? It
works to use it inside other functions. For example:
=================================
> objects <- function(alist) {
for (vars in names(alist))
assign(vars,alist[[vars]],pos=sys.frame(-1))
}
> simple <- function(m,n) {
A=matrix(c(3,3,2,3),2,2)
B=m
c=1:n
list(A=A,B=B,c=c)
}
> rm(A,B,c) #just in case they exist
> stuff=simple(2,3)
> objects(stuff)
> A
[,1] [,2]
[1,] 3 2
[2,] 3 3
> B
[1] 2
> c
[1] 1 2 3
>
=================================
-Scott
*****************************************************************
Scott K. Hyde
Assistant Professor of Statistics and Mathematics
College of Math and Sciences
Brigham Young University -- Hawaii
Laie, HI 96762
On Tue, Jun 2, 2009 at 5:30 PM, Scott Hyde <hy...@byuh.edu> wrote:
>
> I'd like to perform return variable assignments like matlab. For example,
> the following function would return A, B, and c to the script that called it.
>
> =================================
> function [A,B,c] = simple(m,n)
> A=[ 3 2; 3 3]
> B=m
> c=1:n
> =================================
>
> I'd like to do similar assignments in R, but I seem to be able to only return
> one variable. I tried to use a list to return all the arguments, but then
> each has to be referred to using the list. For example:
>
> =================================
> simple <- function(m,n) {
> A=matrix(c(3,3,2,3),2,2)
> B=m
> c=1:n
> list(A=A,B=B,c=c)
> }
>
> > stuff=simple(2,3)
> > stuff
> $A
> [,1] [,2]
> [1,] 3 2
> [2,] 3 3
>
> $B
> [1] 2
>
> $c
> [1] 1 2 3
> =================================
>
> Then I could assign each variable like this (which is what I'd like to avoid):
>
> =================================
> A=stuff$A
> B=stuff$B
> c=stuff$c
> rm(stuff) #stuff isn't needed anymore.
> =================================
>
>
> I've even toyed with the superassignment operator, which also works, but I
> think it doesn't work for functions of functions. The following example
> works.
>
> =================================
> simple2 <- function(m,n) {
> A <<- matrix(c(3,3,2,3),2,2)
> B <<- m
> c <<- 1:n
> }
>
> > stuff2=simple2(2,3)
> > stuff2
> [1] 1 2 3
> > A
> [,1] [,2]
> [1,] 3 2
> [2,] 3 3
> > B
> [1] 2
> > c
> [1] 1 2 3
> =================================
>
> In the example below, I call the function ten inside the function nine. I'm
> expecting that the variable b should change only in the function nine (and
> not in the global environment). In other words, I think the line "(nine) b=
> 9" should be "(nine) b= 10".
>
> Can someone help me know how to do this correctly?
>
> -Scott
>
> =================================
> nine = function(a) {
> b <- 9
> ten(a)
> print(paste("(nine) b=",b))
> }
>
> ten = function(d) {
> b <<- 10
> print(paste("(ten) b=",b))
> print(paste("(ten) d=",d))
> d
> }
>
> > nine(5)
> [1] "(ten) b= 10"
> [1] "(ten) d= 5"
> [1] "(nine) b= 9"
> > b
> [1] 10
> =================================
>
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