Thanks for all of the suggestions. The key key here seems to be using the
"par" function to change the coordinate system like so
plot(rnorm(100), rnorm(100))
op <- par("usr")
par(usr = c(0, 1, 0, 1))
text(0.5,0.5,"TEST")
par(usr = op)
Prof Ripley commented that this approach will also work on log plots, but I
don't think I completely understand what is going on because this does not
work for me
plot(rlnorm(100), rlnorm(100),log="xy")
op <- par("usr")
par(usr = c(0, 1, 0, 1))
text(0.5,0.5,"TEST")
par(usr = op)
Any hints on what I am doing wrong with the log plots? Thanks again for the
help.
Tom