A simplified illustration of the framework of five DCEA methods. A), two expression data matrices from two contrastive experimental conditions (X and Y) involving genes a, b, c, and d, visualized using shades from red (high expression level) to blue (low expression level), are transformed to a pair of coexpression networks. In the coexpression networks, gene pairs with absolute expression correlation values larger than 0.8 are connected with solid lines, while the rest with dashed lines. The line thickness is proportional to the absolute coexpression value. Red color highlights a negative coexpression value, and the grey-shaded node, gene a, is the one whose differential coexpression (dC) calculations are to be illustrated. B), different DCEA methods calculate the dC measure of gene a in different ways (see Results and Discussion for details).