numeric vectors of coordinates where the text labels should be written
labels
a character vector or expression specifying the text to be written
col
foreground text colour
bg
background text colour
theta
position angle offsets for the background shading
r1
shadow width
r2
shadow height
...
additional arguments to be passed to 'text'
Details
'shadowtext' works by plotting the text initially at positions slightly offset from the central position in a darker background colour, and then over-plots the desired text (twice, to avoid anti-aliasing effects).