Turns a normal variable into a reactive variable, that is, one that has
reactive semantics when assigned or read in the usual ways. The variable may
already exist; if so, its value will be used as the initial value of the
reactive variable (or NULL if the variable did not exist).
Usage
makeReactiveBinding(symbol, env = parent.frame())
Arguments
symbol
A character string indicating the name of
the variable that should be made reactive
env
The environment that will contain the reactive
variable