This document discusses environments and scoping in R. It provides examples of how parent environments and parent frames work when calling functions. The key points are: - The parent environment of a function is the environment in which the function is defined. - The parent frame of a function is the environment from which the function was called. - Variables in the parent environments and frames may be accessible depending on the context.

1. R
parent.env parent.frame
Tokyo.Lang.R #0 (2012/02/19)
@a_bicky

2. • Takeshi Arabiki
‣
‣ Twitter & : @a_bicky & id:a_bicky
•
R
•
http://d.hatena.ne.jp/a_bicky/

3. R
Tokyo.R #16 Tsukuba.R #9 R 2011
http://www.slideshare.net/abicky/r-9034336 http://www.slideshare.net/abicky/r-10128090 http://www.slideshare.net/abicky/rtwitter

4. R
• R
• parent.env parent.frame
•
•

5. R
• R
• parent.env parent.frame
•
•

6. R

7. “ ”

8. ←R
“ ”

9. > x <- "x of R_GlobalEnvn"
> f <- function() {
+ x <- "x of function fn"
+ g()
+ # f x
+ h <- function() cat("h:", x)
+ h()
+ }
> # R_GlobalEnv x
> g <- function() cat("g:", x)
> f() # f g, h
g: x of R_GlobalEnv
h: x of function f
> g() # g
g: x of R_GlobalEnv

10. > x <- "x of R_GlobalEnvn"
> # parent.frame()
> f <- function() {
+ x <- "x of function fn"
+ g()
+ # f f x
+ h <- function() cat("h:", evalq(x, parent.frame()))
+ h()
+ }
> # x
> g <- function() cat("g:", evalq(x, parent.frame()))
> f() # f g, h
g: x of function f
h: x of function f
> g() # g
g: x of R_GlobalEnv

11. R
(enclosing environment)
> x <- 1; y <- 1 R_GlobalEnv
> f <- function(x) print(x) x = 1
> f(2) y = 1
[1] 2
f
x = 2

12. parent.env parent.frame
parent.env
enclosing environment
parent.frame
caller’s environment

13. parent.env parent.frame
parent.env
enclosing environment
parent.frame
caller’s environment

14. > f <- function() {
+ g()
+ }
> g <- function() {
+ h1()
+ h2()
+ }
> h1 <- function() NULL
> h2 <- function() NULL
>

15. > f <- function() {
+ g()
+ }
> g <- function() {
+ h1()
+ h2()
+ }
> h1 <- function() NULL
> h2 <- function() NULL
> f()
f f()

16. > f <- function() {
+ g()
+ }
> g <- function() {
+ h1()
+ h2()
+ }
> h1 <- function() NULL
> h2 <- function() NULL callee g
g()
> f()
caller f

17. > f <- function() {
+ g()
+ }
> g <- function() {
+ h1()
+ h2()
+ }
callee h1
h1()
> h1 <- function() NULL
> h2 <- function() NULL caller g
> f()
f

18. > f <- function() {
+ g()
+ }
> g <- function() {
+ h1()
+ h2()
+ }
> h1 <- function() NULL
> h2 <- function() NULL g
> f()
f

19. > f <- function() {
+ g()
+ }
> g <- function() {
+ h1()
+ h2()
+ }
callee h2
h2()
> h1 <- function() NULL
> h2 <- function() NULL caller g
> f()
f

20. > f <- function() {
+ g()
+ }
> g <- function() {
+ h1()
+ h2()
+ }
> h1 <- function() NULL
> h2 <- function() NULL g
> f()
f

21. > f <- function() {
+ g()
+ }
> g <- function() {
+ h1()
+ h2()
+ }
> h1 <- function() NULL
> h2 <- function() NULL
> f()
f

22. > f <- function() {
+ g()
+ }
> g <- function() {
+ h1()
+ h2()
+ }
> h1 <- function() NULL
> h2 <- function() NULL
> f()
NULL

23. R
• R
• parent.env parent.frame
•
•

24. parent.env parent.frame

25. parent.env parent.frame
parent.env
enclosing environment
parent.frame
caller’s environment

26. parent.env 1
> f <- function() {
+ e <- environment()
+ cat("environment of f: "); print(e)
+ cat("parent environment of f: "); print(parent.env(e))
+ g <- function() { # f g
+ e <- environment()
+ cat("environment of g: "); print(e)
+ cat("parent environment of g: "); print(parent.env(e))
+ }
+ g()
+ }
> f()
environment of f: <environment: 0x105acb7c0>
parent environment of f: <environment: R_GlobalEnv>
environment of g: <environment: 0x105acf228>
parent environment of g: <environment: 0x105acb7c0>

27. parent.env 1
> f <- function() {
+ e <- environment()
+ cat("environment of f: "); print(e)
+ cat("parent environment of f: "); print(parent.env(e))
+ g <- function() { # f g
+ e <- environment()
+ cat("environment of g: "); print(e)
+ cat("parent environment of g: "); print(parent.env(e))
+ }
+ g()
+ } f parent.env R_GlobalEnv g parent.env f
> f()
environment of f: <environment: 0x105acb7c0>
parent environment of f: <environment: R_GlobalEnv>
environment of g: <environment: 0x105acf228>
parent environment of g: <environment: 0x105acb7c0>

28. parent.env 2
> f <- function() {
+ e <- environment()
+ cat("environment of f: "); print(e)
+ cat("parent environment of f: "); print(parent.env(e))
+ g()
+ }
> g <- function() { # f R_GlobalEnv g
+ e <- environment()
+ cat("environment of g: "); print(e)
+ cat("parent environment of g: "); print(parent.env(e))
+ }
> f()
environment of f: <environment: 0x105adbad0>
parent environment of f: <environment: R_GlobalEnv>
environment of g: <environment: 0x105adf638>
parent environment of g: <environment: R_GlobalEnv>

29. parent.env 2
> f <- function() {
+ e <- environment()
+ cat("environment of f: "); print(e)
+ cat("parent environment of f: "); print(parent.env(e))
+ g()
+ }
> g <- function() { # f R_GlobalEnv g
+ e <- environment()
+ cat("environment of g: "); print(e)
+ cat("parent environment of g: "); print(parent.env(e))
+ } f parent.env g parent.env R_GlobalEnv
> f()
environment of f: <environment: 0x105adbad0>
parent environment of f: <environment: R_GlobalEnv>
environment of g: <environment: 0x105adf638>
parent environment of g: <environment: R_GlobalEnv>

30. parent.frame 1
> f <- function() {
+ e <- environment()
+ cat("environment of f: "); print(e)
+ cat("parent environment of f: "); print(parent.frame())
+ g <- function() { # f g
+ e <- environment()
+ cat("environment of g: "); print(e)
+ cat("parent environment of g: "); print(parent.frame())
+ }
+ g()
+ }
> f()
environment of f: <environment: 0x105ae7670>
parent environment of f: <environment: R_GlobalEnv>
environment of g: <environment: 0x105aeb110>
parent environment of g: <environment: 0x105ae7670>

31. parent.frame 1
> f <- function() {
+ e <- environment()
+ cat("environment of f: "); print(e)
+ cat("parent environment of f: "); print(parent.frame())
+ g <- function() { # f g
+ e <- environment()
+ cat("environment of g: "); print(e)
+ cat("parent environment of g: "); print(parent.frame())
+ }
+ g()
+ } f parent.frame R_GlobalEnv g parent.frame f
> f()
environment of f: <environment: 0x105ae7670>
parent environment of f: <environment: R_GlobalEnv>
environment of g: <environment: 0x105aeb110>
parent environment of g: <environment: 0x105ae7670>

32. parent.frame 2
> f <- function() {
+ e <- environment()
+ cat("environment of f: "); print(e)
+ cat("parent environment of f: "); print(parent.frame())
+ g()
+ }
> g <- function() { # f R_GlobalEnv g
+ e <- environment()
+ cat("environment of g: "); print(e)
+ cat("parent environment of g: "); print(parent.frame())
+ }
> f()
environment of f: <environment: 0x105aef440>
parent environment of f: <environment: R_GlobalEnv>
environment of g: <environment: 0x105aee7c0>
parent environment of g: <environment: 0x105aef440>

33. parent.frame 2
> f <- function() {
+ e <- environment()
+ cat("environment of f: "); print(e)
+ cat("parent environment of f: "); print(parent.frame())
+ g()
+ }
> g <- function() { # f R_GlobalEnv g
+ e <- environment()
+ cat("environment of g: "); print(e)
+ cat("parent environment of g: "); print(parent.frame())
+ } f parent.frame R_GlobalEnv g parent.frame f
> f()
environment of f: <environment: 0x105aef440>
parent environment of f: <environment: R_GlobalEnv>
environment of g: <environment: 0x105aee7c0>
parent environment of g: <environment: 0x105aef440>

34. > x <- "x of R_GlobalEnv" R_GlobalEnv
> f <- function() {
+ x <- "x of function f" x = "x of R_GlobalEnv"
+ g <- function() {
+ cat("x in g:", x, "n")
+ }
+ g(); h() f
+ }
x = "x of function f"
> h <- function() {
+ cat("x in h:", x, "n")
+ }
>
g h

35. > x <- "x of R_GlobalEnv" R_GlobalEnv
> f <- function() {
+ x <- "x of function f" x = "x of R_GlobalEnv"
+ g <- function() {
+ cat("x in g:", x, "n")
+ }
+ g(); h() f
+ }
x = "x of function f"
> h <- function() {
+ cat("x in h:", x, "n")
+ }
> f()
g h

36. > x <- "x of R_GlobalEnv" R_GlobalEnv
> f <- function() {
+ x <- "x of function f" x = "x of R_GlobalEnv"
+ g <- function() {
+ cat("x in g:", x, "n")
+ }
+ g(); h() f
+ }
x = "x of function f"
> h <- function() {
+ cat("x in h:", x, "n")
+ } g()
> f()
x in g: x of function f g h
parent.env parent.frame

37. > x <- "x of R_GlobalEnv" R_GlobalEnv
> f <- function() {
+ x <- "x of function f" x = "x of R_GlobalEnv"
+ g <- function() {
+ cat("x in g:", x, "n")
+ }
+ g(); h() f
+ }
x = "x of function f"
> h <- function() {
+ cat("x in h:", x, "n")
h()
+ }
> f()
x in g: x of function f g h
x in h: x of R_GlobalEnv
parent.frame parent.env

38. R
• R
• parent.env parent.frame
•
•

40. > search() # R_GlobalEnv base package
[1] ".GlobalEnv" "package:stats" "package:graphics"
[4] "package:grDevices" "package:utils" "package:datasets"
[7] "package:methods" "Autoloads" "package:base"
> attach(iris); search() # iris 2
[1] ".GlobalEnv" "iris" "package:stats"
[4] "package:graphics" "package:grDevices" "package:utils"
[7] "package:datasets" "package:methods" "Autoloads"
[10] "package:base"
> parent.env(globalenv()) # 2 R_GlobalEnv
<environment: 0x100cd62b0>
attr(,"name")
[1] "iris"

41. > x <- "x of R_GlobalEnv" base package
> l <- list(y = "y of l") .Last.value
> attach(l)
>
l
y = "y of l"
R_GlobalEnv
x = "x of R_GlobalEnv"
l = list(y = "y of l")

42. > x <- "x of R_GlobalEnv" base package
> l <- list(y = "y of l") .Last.value
> attach(l)
> x
[1] "x of R_GlobalEnv"
>
l
y = "y of l"
R_GlobalEnv
x = "x of R_GlobalEnv"
l = list(y = "y of l")

43. > x <- "x of R_GlobalEnv" base package
> l <- list(y = "y of l") .Last.value
> attach(l)
> x
[1] "x of R_GlobalEnv"
> y
[1] "y of l" l
> y = "y of l"
R_GlobalEnv
x = "x of R_GlobalEnv"
l = list(y = "y of l")

44. > x <- "x of R_GlobalEnv" base package
> l <- list(y = "y of l") .Last.value
> attach(l)
> x
[1] "x of R_GlobalEnv"
> y
[1] "y of l" l
> .Last.value y = "y of l"
[1] "y of l"
>
R_GlobalEnv
x = "x of R_GlobalEnv"
l = list(y = "y of l")

45. > x <- "x of R_GlobalEnv" base package
> l <- list(y = "y of l") .Last.value
> attach(l)
> x
[1] "x of R_GlobalEnv"
> y
[1] "y of l" l
> .Last.value y = "y of l"
[1] "y of l"
> y <- "y of R_GlobalEnv"
> R_GlobalEnv
x = "x of R_GlobalEnv"
l = list(y = "y of l")
y = "y of R_GlobalEnv"

46. > x <- "x of R_GlobalEnv" base package
> l <- list(y = "y of l") .Last.value
> attach(l)
> x
[1] "x of R_GlobalEnv"
> y
[1] "y of l" l
> .Last.value y = "y of l"
[1] "y of l"
> y <- "y of R_GlobalEnv"
> y R_GlobalEnv
[1] "y of R_GlobalEnv" x = "x of R_GlobalEnv"
l = list(y = "y of l")
y = "y of R_GlobalEnv"

47. > counter <- function(cnt) {
+ function() { # <<-
+ cnt <<- cnt + 1; print(cnt)
+ }
+ }
> c1 <- counter(1); c1 #
function() {
cnt <<- cnt + 1; print(cnt)
}
<environment: 0x1020374a0>
> ls.str(environment(c1)) # cnt
cnt : num 1
> c1(); c1() # cnt
[1] 2
[1] 3

48. > counter <- function(cnt) { R_GlobalEnv
+ function() {
+ cnt <<- cnt + 1
+ print(cnt) counter(1)
+ }
counter
+ }
> c1 <- counter(1) cnt = 1
>
c1

49. > counter <- function(cnt) { R_GlobalEnv
+ function() {
+ cnt <<- cnt + 1
+ print(cnt)
+ }
counter
+ }
> c1 <- counter(1) cnt = 2
> c1()
c1()
[1] 2
c1

50. > counter <- function(cnt) { R_GlobalEnv
+ function() {
+ cnt <<- cnt + 1
+ print(cnt)
+ }
counter
+ }
> c1 <- counter(1) cnt = 3
> c1()
c1()
[1] 2
> c1() c1
[1] 3

51. R
• R
• parent.env parent.frame
•
•

53. • R
• parent.env
enclosing environment
• parent.frame
caller’s environment
•
•

54. • R Language Definition http://cran.r-project.org/doc/manuals/R-lang.pdf
2.1.10 Environment, 3.5 Scope of variables, 4.3.4 Scope
• R Internals http://cran.r-project.org/doc/manuals/R-ints.pdf
1.2 Environments and variable lookup
• Frames, Environments, and Scope in R and S-PLUS
http://cran.r-project.org/doc/contrib/Fox-Companion/appendix-scope.pdf
• ,R , C&R , 2012
SECTION 208, 209
• U. ( ), ( ), R ,
, 2006
4.3
• R http://www.slideshare.net/shuyo/r-4022379
• environment http://user.ecc.u-tokyo.ac.jp/~s105503/p02.html