How to position annotate text in the blank area of facet ggplot

Question

How to annotate some text in the blank space within a odd numbered faceted ggplot. Lets have a faceted ggplot with data as below with with 2 rows and 2 columns. So there is

Answer 1

After you create your plot, simply use

print(facetplot)
grid.text("your text", x = 0.75, y = 0.25)

See ?grid.text for details on positioning. The default coordinate system is the entire screen device with (0,0) as the lower left and (1,1) as the upper right.

Answer 2

To modify the graphical parameter setting for grid.text such as font color, family, fontface and size ...

grid.text("your text", x = 0.6, y = 0.15, gp = gpar(col="red", fontsize = 20, family = "Times", fontface = "italic"))