How to use the value of a variable as key in an R-environment?

Question

In R programming language I want to use a hash table.

How do I use the value of a variable as the key for the environment?

For example:

map &         


        

Answer 1

As it says in ?"$":

 Both ‘[[’ and ‘$’ select a single element of the list.  The main
 difference is that ‘$’ does not allow computed indices, whereas
 ‘[[’ does.  ‘x$name’ is equivalent to ‘x[["name", exact =
 FALSE]]’.  Also, the partial matching behavior of ‘[[’ can be
 controlled using the ‘exact’ argument.

So you want:

map[[key]] <- 4
> print(ls(map))
[1] "ffffd" "key"
> map[[key]]
[1] 4