Statistics and Data Analysis for Microarrays Using R and Bioconductor, 2nd Edition

Data preprocessing and n ormalization 711

FIGURE 20.8: LOWESS normaliza tion. A scatter plot before (left panel)

and after (right panel) the LOWESS correction. The horizontal axis represents

log

2

(cy3) and the vertical axis represe nts log

2

(cy5).

data a nalysis and taking into consideration the availability of powerful and

cost effective computer hardware. A more important disadvantage is related

to LO(W)ESS’s susceptibility to noise and outliers. More robust versions of

LO(W)ESS have been proposed [100], but even the robust version may be

disrupted by e xtreme outliers. This is one of the reasons for which outliers

(e.g., flagged spots) s hould be remov ...