Expose the names in
lhs to the
rhs expression. This is useful when functions
do not have a built-in data argument.
A list, environment, or a data.frame.
An expression where the names in lhs is available.
Some functions, e.g.
aggregate, have a
data argument, which allows the direct use of names inside the data as part
of the call. This operator exposes the contents of the left-hand side object
to the expression on the right to give a similar benefit, see the examples.