Plot with nested x-labels

Antje wrote:

Hi there,

I was wondering wether it is possible to creeate plots with nested 
lables like in excel?
If yes, could anyone provide me the information how to do it?
I've attached an image of an Excel plot to show you, what I'd like to 
plot with R :-)

Hi Antje,
The very question asked by Ofir Levy that led to the new hierobarp 
function in the plotrix package.

Jim