Masses, radii, densities, and period ratios of adjacent planets. The scatter graph for mass (top left), radius (top right), and density (bottom left) of a planet against the same parameter of the next planet farther from the star is plotted with observational errors indicated by the grey lines. The bottom right panel shows the period ratio between the middle and inner planet against that between the outer and middle planet in triples. The blue and red dot-shaped markers correspond to the sample and Solar System planet pairs, respectively. The black dashed line is the 1:1 line. The observational errors could be smaller than the marker size. In the bottom right corner of each plot, the cumulative distribution function is plotted for the decimal logarithm of each planet parameter ratio (x-axis) versus counts (y-axis). In these subplots, the black vertical dashed line is unity and the red horizontal dashed line is where the cumulative distribution function reaches the 50th percentile.