Hi Peter and Don, unless you have an actual reason for only caring about the East-West axis, rather than all directions, you should include both cos and sin: cos(exposure*PI/180) and sin(exposure*PI/180) as Jeffrey originally suggested. [or more generally, cos(exposure*2*PI/T) and sin(exposure*2*PI/T) where T is the period of your circular variable]
Geometrically, this maps the variable onto the unit circle (or in this case perhaps we should call it the unit compass?). All the best David ______________________________________________________ David Warton Associate Professor and Australian Research Council Future Fellow School of Mathematics and Statistics and the Evolution & Ecology Research Centre The University of New South Wales NSW 2052 AUSTRALIA phone (61)(2) 9385-7031 fax (61)(2) 9385-7123 http://www.eco-stats.unsw.edu.au [[alternative HTML version deleted]] _______________________________________________ R-sig-ecology mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
