Hi. I am looking for a function to calculate unusual ratio (also known as Z score transformation) for identification of differentially expressed genes with Affymetrix data. Regards Anthony -- ______________________________________________ Anthony Bosco - Cell Biology Research Assistant Institute for Child Health Research (Company Limited by Guarantee ACN 009 278 755) Subiaco, Western Australia, 6008 Ph 61 8 9489 , Fax 61 8 9489 7700 email anthonyb@ichr.uwa.edu.au