Recently, I was trying to make an inward-facing label for a vertical
axis on the right-hand side of a plot. The inward-facing label was
required by a journal. I searched R-help, but the only solution I found
was to use text, which requires fiddling with the x-coordinate for each
plot. What would have been perfect is a way to rotate text in mtext.
I had a similar problem trying to use mtext to put a vertical label on a
vertical axis with horizontal tick labels.
Jonathan Dushoff