Text Contrast in a Plot

Hi List,

I would appreciate any suggestion on how can I make a text I?ve inserted in
a plot show some contrast? With this I mean that I have a white text on a
plot and I would like to make a tiny border around it in black, so even
being small sized and the entire graphic being small in the text page I?ll
insert it. It will be visible.

 

Well I tried inserting a box() function inside the text() function, R
accepts the command but there is no effect. I even tried to plot a greater
black text and then a smaller white one at the same place, but it doesn?t
look good.