
752 Statistics and Data Analysis for Microarrays Using R and Bioconductor
FIGURE 21.1: Fold change on a histogram. Ex periment-control ratios can
be plotted as a histogram showing the number of genes (vertical axis) for
every ratio value (horizontal axis). The horizontal axis is graded in fold-change
units. Selecting differentially regulated genes based on fold change corresponds
to se le cting the genes in the tails of the histogram (blue areas) by setting
thresholds at the desired minimum fold change. Note the resemblance of this
figure with Fig. 11.5 in Chapter 11.
gene differentially regulated by mistake) while in the fold change method, the
thresholds ...