[R] Gridbase basic question

[Sean Davis]

All,

I have a simple plot(x,y) and I would like to then insert rectangles of  
some length (in native coordinates) and height fixed to 0.5 in native  
coordinates.  I can't quite get the code right to do this.  Can anyone  
give me a quick example of how to do this?  I looked the gridBase index  
and the tutorial (from R-news?) but just haven't gotten it down yet.

 > plot(1:10,1:10)
 > par(new=T);vps <- baseViewports()
 > pushViewport(vps$inner,vps$figure,vps$plot)
viewport[GRID.VP.28]
 > pushViewport(viewport(x=unit(1,"native"),y=unit(2,"native")))
viewport[GRID.VP.29]
 >  
grid.rect(height=unit(0.5,"native"),width=unit(1.5,"native"),just='botto 
m')

This draws a very large rectangle going from 2 to 7 (y) and to 8 (x).

Thanks,
Sean