Hi all,

I need to put two different axis to one plot. On the top of the plot, I need
to put one axis, with increments from left side to the right side; then at
the bottom of the same plot, I need to put another axis, with increments
from right side to the left side and showing a different unit. How do I do
that?

By the way, is there a "hold" command for plotting?

If I first plot a picture, how to add another "plot" command onto it without
erasing it?

In matlab, it can be convinient done by "hold on" and "hold off"... and can
I do it in R?

Thanks a lot,

Micheal

	[[alternative HTML version deleted]]


