Hi, I'm trying out different combinations of normalisation and expression summaries on some affy data using expresso and am confused by the comment in the expresso help file about having to scale mas-summarised values after running expresso. Is this just for compatibility with mas software or are some of the normalisation methods not applicable to probe-level data? Does the affy.scalevalue.exprSet method just perform the eqivalent of the expresso constant normalisation, but on expression summaries rather than probe- level data or am I missing something? Apologies if this is a dumb question Cassxx. ------------------------------------------------- This mail sent through UCL Biochemistry's Webmail: http://webmail.biochem.ucl.ac.uk/ (unsecured) https://webmail.biochem.ucl.ac.uk/ (secured)