Fig. 7
From: Integrating mean and variance heterogeneities to identify differentially expressed genes
Global data structure of all the experiment-wide gene expression levels. Using MAS5, we normalized the raw expression levels of the 22,283 experiment-wide gene probes and computed the PCs of all the normalized expression levels. PC1 alone accounted for 98.24% of the total variation and was the unique major PC. PC2 merely accounted for 0.32% of total variation. Neither PC1 nor PC2 displayed mean heterogeneity or variance heterogeneity. PC4 displayed strikingly significant mean heterogeneity (p WT  = 1.91 × 10− 15), even if it only accounted for 0.13% of the total variation. PC6 displayed very significant variance heterogeneity (p LF  = 3.18 × 10− 4) even if it accounted for 0.07% of the total variation only. PC4 and PC6 clearly distinguished the smokers and the nonsmokers. a Variation proportions, b PC1 and PC2, c PC4 and PC6