May I ask for a pointer to documentation of how to use category data (text categories), which I would like to graph as present/absent at stations along a transect. Thanks for any pointers, Alan Davis -- adavis at saipan.com 1-670-322-6580 Alan E. Davis, PMB 30, Box 10006, Saipan, MP 96950-8906, CNMI I have steadily endeavored to keep my mind free, so as to give up any hypothesis, however much beloved -- and I cannot resist forming one on every subject -- as soon as facts are shown to be opposed to it. -- Charles Darwin (1809-1882) The right to search for truth implies also a duty; one must not conceal any part of what one has recognized to be true. -- Albert Einstein As we enjoy great advantages from the inventions of others we should be glad of an opportunity to serve others by any invention of ours, and this we should do freely and generously. -- Benjamin Franklin