[R] To package or not to package?

[Carl Witthoft]

I'd like a little advice as to when it's appropriate to create an 
R-package and submit it, as opposed to just providing the source to some 
simple code.
In this case, I've written a function that draws a line plot (with 
options for points, etc) where the color of the line changes at 
specified values of the y-data (e.g., it's one color below -10, another 
color between -10 and -5, etc).  It's pretty clean, and has a few 
error-checks, self-correctors, etc., so I would be happy to provide it 
to the community as a whole.
So, is this worthy of a package, or should I just post the function code 
(well commented)?
Or is this feature available deep inside some graphing package I haven't 
found yet? :-(

thanks for all advice.
Carl