How to annotate across or between plots in multi-plot panels in R

Question

If I have several plots in a single panel, I would like to be able to put text annotations that go across more than one plot area or that go in between plot areas. I\'m sure

Answer 1

Here is an example using Greg Snow's approach:

par(mfrow=c(2, 2))
replicate(4, plot(matrix(runif(20), nrow=10)))
text(grconvertX(.5, "ndc", "user"), grconvertY(.25, "ndc", "user"), "TEST", cex=3, col="red", xpd=NA)
text(grconvertX(.5, "ndc", "user"), grconvertY(.75, "ndc", "user"), "TEST", cex=3, col="red", xpd=NA)