(optional) Additional named options specified as a named list.
envir
The environment in which the expression should be evaluated.
Author
Henrik Bengtsson
Details
Upon exit (also on errors), this function will reset all
(modifiable) graphical parameters to the state of options available
upon entry. This means any parameters modified from evaluating
expr will also be undone upon exit.
See Also
Internally, eval() is used to evaluate the expression,
and par to set graphical parameters.