\begin{Schunk}
\begin{Sinput}
 old.par <- par(no.readonly = TRUE)
 ## make your changes to par
 par(xpd = TRUE, mar = c(3, 4, 1, 2))
 ## make desired figure. When done, restore device.
 par(old.par)
\end{Sinput}
\end{Schunk}
