Plotting direction vectors from an aspect map

R-sig-geo'ers:

Given an aspect raster (GDAL-readable), is there a way to plot the
aspect image using arrows representing each cell's direction?  I'm
assuming I have to convert the raster to a set of points -- are there
arrow symbols and, if so, can you rotate them based on some parameter?

Thanks!

--j

Jonathan A. Greenberg, PhD
Assistant Project Scientist
Center for Spatial Technologies and Remote Sensing (CSTARS)
Department of Land, Air and Water Resources
University of California, Davis
One Shields Avenue
Davis, CA 95616
Phone: 415-763-5476
AIM: jgrn307, MSN: jgrn307 at hotmail.com, Gchat: jgrn307