duplicate() is an interface to the C-level duplicate() and
shallow_duplicate() functions. It is mostly meant for users of
the C API of R, e.g. for debugging, experimenting, or prototyping C
code in R.
     
    
    Usage
    duplicate(x, shallow = FALSE)
 
     
    
    Arguments
- x
 
An R object. Uncopyable objects like symbols and
environments are returned as is (just like with <-).
 
- shallow
 
Recursive data structures like lists, calls and
pairlists are duplicated in full by default. A shallow copy only
duplicates the top-level data structure.