Dear all, I want to obtain the Standard Error of the signals given by RMA. I can do this with the se.exprs() function after performing the expresso() function on my data. My problem is that this does not work on a large number of arrays (n=111), because I cannot even read the data; I have the following: ------------------------------------------- > raw <- ReadAffy() Error: cannot allocate vector of size 439615 Kb ------------------------------------------- even if I maximize the memory available for R to run with the line: --max-mem-size=3000M So my question is: do you know another way for me to obtain the SE of the given signals by RMA ? Thanks a lot for your help, Florence.