[BioC] ratios in SAM analysis

[Flora Fan]

Hi all,

I have a question about working with ratios in SAM analysis. I have 8 CEL
files, C1,C2...C8 in one AffyBatch file, called CEL.Batch and I would like
to do the two class (unpaired) SAM analysis between two groups of ratios:
    group1: C1/C2 and C3/C4 (duplicates)
    group2: C5/C6 and C7/C8 (duplicates),

How can I get the ratio of two columns of an AffyBatch file? and how
to make the result acceptable to SAM?

Any suggestion would be greatly appreciated.

Fan