I downloaded CEL files from Gene Omnibus. I usually get the gene expression values using the R affy library and the function expresso. Unfortunately those CEL files are associated to the Exon Array that can't be processed by expresso. After a research on google I found the aroma package. Apparently this should help me to get what I need, but I couldn't find a simple tutorial that illustrate step by step how to convert CEL files to expression values. Can somebody point me a simple (I'm quite new about R) tutorial/example?