Dear All, I am trying to fit a model with covariates that are observed only above a certain value. As I understand I canot use "I". I was wondering whether anyone had a script that I could use as a guideline. Many thanks Alessandra Cervino MSc, DPhil Principal Research Statistician Oxford Glycosciences (UK) Ltd 10, The Quadrant Abingdon Science Park Abingdon OX14 3YS Tel: 01235 543200 ext 7744 Fax: 01235 554701 ********************************************************************** The information transmitted by this email is private and confidential and is intended for the use of the intended recipients specified therein. If you are neither an intended recipient nor an employee or agent responsible for delivery to an intended recipient, you should be aware that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately. ********************************************************************** %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%