Variables declared inside a function are local to that function. For instance:
foo <- function() {
bar <- 1
}
foo()
bar
gives the following error: Error: object 'bar' not found.
If you want to make bar a global variable, you should do:
foo <- function() {
bar <<- 1
}
foo()
bar
In this case bar is accessible from outside the function.
However, unlike C, C++ or many other languages, brackets do not determine the scope of variables. For instance, in the following code snippet:
if (x > 10) {
y <- 0
}
else {
y <- 1
}
y remains accessible after the if-else statement.
As you well say, you can also create nested environments. You can have a look at these two links for understanding how to use them:
Here you have a small example:
test.env <- new.env()
assign('var', 100, envir=test.env)
# or simply
test.env$var <- 100
get('var') # var cannot be found since it is not defined in this environment
get('var', envir=test.env) # now it can be found