The global phase-shift statistics distribution for the APGs of the cell cycle regulatory network (totally 83 pairwise candidates in APGs). The phase-shift statistics vary as functions of the gain thresholds. The blue bold curve represents the integral tendency of gene pairs with leading phase shifts (positive), the red for the pairs with lagging phase shifts (negative), and the green for those without detected phase shift (undirected), i.e. there might be no regulatory activities between corresponding gene pairs (the same as in following figures). Through dynamic gain thresholding, we may easily determine concrete regulatory time lags, regulatory directions and signal intensities from the quantitative signal processing perspective.