R - Create a separate environment where to source() an R script, such that the latter does not affect the "caller" environment

Question

Scenario: Let's say I have a master pipeline.R script as follows:

WORKINGDIR="my/master/dir" 
setwd(WORKINDIR)

# Step 1
tA = Sys.time()
source("step1.R")
difftime(Sys.time(), tA)

# Add as many steps as desired, ... 

And suppose that, within step1.R happens a:

rm(list=ls())

Question: How can I separate the pipeline.R (caller) environment from the step1.R environment? More specifically, I would like to run step1.R in separate environment such that any code within it, like the rm, does not affect the caller environment.

Answer 1

There are a few ways to call a R script and run it. One of them would be source().

Source evaluates the r script and does so in a certain environment if called so. Say we have a Test.R script:

#Test.R
a <- 1    
rm(list = ls())
b <- 2
c <- 3

and global variables:

a <- 'a'
b <- 'b'
c <- 'c'

Now you would like to run this script, but in a certain environment not involving the global environment you are calling the script from. You can do this by doing creating a new environment and then calling source:

step1 <- new.env(parent = baseenv())

#Working directory set correctly.
source("Test.R", local = step1)

These are the results after the run, as you can see, the symbols in the global environment are not deleted.

a
#"a"
b
#"b"
step1$a
#NULL
#rm(list = ls()) actually ran in Test.R
step1$b
#2

Note: You can also run a R script by using system. This will, however, be ran in a different R process and you will not be able to retrieve anything from where you called the script.

system("Rscript Test.R")