
726 Statistics and Data Analysis for Microarrays Using R and Bioconductor
8. Combine the replicate values to calculate a mean/median/mode value
and the standard deviation.
For Affymetrix data, we recommend the use o f the simplyaffy package in
Bioconductor for the preproce ssing and normalization. Exa mples illustrated
how to use various functions from this and other related packages follow later
in this chapter, as well as the next chapter. A viable alternative for the pre -
processing is the dChip package implementing the model proposed by Wong
et al. (Eq. 20.41).
If the data are available as average differences (as from older versions of
the Affymetrix ...