Mean R of neighboring gene pairs in different -lg p -value intervals. Mean R values of neighboring gene pairs in -lg p intervals. All p-values were calculated with D = 25K. Gene pairs grouped into parallel, divergent, and convergent orientations are plotted similarly. There is only one gene pair has -lg p-value in the interval 5~6, for both the divergent and convergent cases. They are hence omitted from the plot.