Finding the "height of a line of text" for axis

Thanks for your reply.

or even something like this:

 plot(1:5, axes = FALSE)
 axis(1, col.axis = "white", col = "red", tcl = 1)
 axis(1, col.axis = "white", col = "white", tcl = 0)
 axis(2, col.axis = "white", col = "red", tcl = 1)
 axis(2, col.axis = "white", col = "white", tcl = 0)

This is the effect I am trying to achieve. I did try the route of
overdrawing in white, but decided against it. The reason I haven't
used that, is that firstly I wasn't sure if there would be some
rounding error in a printer which would cause the background to
appear. Secondly, the end of the ticks look weird due to the different
line end types:
 http://www.cl.cam.ac.uk/users/sjm217/volatile/r-lineend.png

Changing to square caps might help, but I was hoping there would be a
nice solution that would let me keep round caps. Any suggestions?

Thank you,
Steven Murdoch.

w: http://www.cl.cam.ac.uk/users/sjm217/