Hi This is obviously a wider problem, I think, than simply within limma, where I found it. The command: Michael Watson Head of Informatics Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berkshire RG20 7NN UK Phone : +44 (0)1635 578411 ext. 2535 Mobile: +44 (0)7990 827831 E-mail: michael.watson at bbsrc.ac.uk