[BioC] fold change after gcrma()

yotsawat pomyen yotsa at yahoo.com
Mon Jun 13 15:46:02 CEST 2011

Dear All, 

I normalised and summarised my data using gcrma() routine and have the 
expression values for each probeset. I now want to do the comparison between two 
classes of the samples (i.e. fold change between the classes). One thing I'm not 
sure is how to compare them because, as I read from the gcrma paper, the 
expression values after the gcrma() routine are log(intensity) after background 

My question is: Do I have to convert the expression values from gcrma() back to 
raw values by e^(values) before calculate the fold change between the two 
classes that I have? 



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