[BioC] 3' 5' ratio

[Sylvia Merk]

Hi all,

I have cel-files from Affymetrix U133a+b chips and I wanted to do some 
quality control - so I read in the cel-files with the affy-package  and 
got an affybatch-object.
Then I had a look at the RNA degradation plots. I know that Microarray 
suite performs 3'/5'-ratios as a quality check. My problem is: I've only 
got the cel-files - there is no other information from Microarray suite 
available. So my question is: is it possible to calculate  3'/5'-ratios 
out of the cel-file?
Thank you in advance for your help.

Many greetings
Sylvia