[R] behaviour of formula objects and environment inside functions

[Thomas Alexander Gerds]

Dear List

I am looking for the recommended way to create a formula inside a
function with an empty environment. I tried several versions (see
below), and one of them seemed to work, but I dont understand why there
is a difference between .GlobalEnv and the environment inside a
function. I would be greatful for any reference or explanation or
advice.

Thanks
Thomas

#+BEGIN_SRC R  :results output raw  :exports results  :session *R* :cache yes 
  test0 <- function(x){
    x <- rnorm(1000000)
    out <- list()
    out$f <- as.formula(u~b,env=NULL)
    out
  }
  test1 <- function(x){
   x <- rnorm(1000000)
    out <- list(f=formula(u~b))
    environment(out$f) <- NULL
    out
  }
  test2 <- function(x){
   x <- rnorm(1000000)
    out <- list(f=as.formula(u~b,env=emptyenv()))
    out
  }
  v0 <- test0(1)
  v1 <- test1(1)
  v2 <- test2(1)
  x <- rnorm(1000000)
  v3 <- formula(u~b)
  save(v0,file="~/tmp/v0.rda")
  save(v1,file="~/tmp/v1.rda")
  save(v2,file="~/tmp/v2.rda")
  save(v3,file="~/tmp/v3.rda")
  system("ls -lah ~/tmp/v*.rda")
#+END_SRC

#+RESULTS[<2013-03-20 18:56:26> 0dca0a85fb6472b0250968c3d42527ca0310f86e]:
-rw-rw-r-- 1 tag tag 7,4M Mar 20 18:56 /home/tag/tmp/v0.rda
-rw-rw-r-- 1 tag tag  111 Mar 20 18:56 /home/tag/tmp/v1.rda
-rw-rw-r-- 1 tag tag 7,4M Mar 20 18:56 /home/tag/tmp/v2.rda
-rw-rw-r-- 1 tag tag  113 Mar 20 18:56 /home/tag/tmp/v3.rda

--
Thomas A. Gerds -- Assoc. Prof. Department of Biostatistics
University of Copenhagen, Øster Farimagsgade 5, 1014 Copenhagen, Denmark
Office: CSS-15.2.07 (Gamle Kommunehospital)
tel: 35327914 (sec: 35327901)