After my recent article on marking deprecated code in Python, I had to do the same thing in R. It's included in the language (in The R Base Package).

To deprecate an object simply make a call to the .Deprecated() function. It will produce a warning—that can be suppressed by users by calling suppressWarnings().

It's also possible to signal that an object has been removed through a call to .Defunct(). In this case it will produce an error, in other terms the program will stop working.

old_function <- function() {
    .Deprecated(msg = "Will be removed in the next version")
    cat("\nI'm old now I want to retire...")

dead_function <- function() {
    .Defunct(msg = "Function removed :-(")
    cat("\nI'm dead now I will not chat anymore...")

# Will be removed in the next version
# I'm old now I want to retire...

# Error : Function removed :-(

References / Further reading