Correlations for 14 pairs of activity indices listed in Table 6 (not shown: R_IRT–[Li/H], which has a negligible correlation coefficient). Text in the lower-left corner of each plot indicates the pair of indices; the x-axis (y-axis) plots the first (second) index listed. The lower-right corner lists the Spearman correlation coefficients from Table 6. For convenience, squares at the start of each row of coefficients correspond to squares in the upper-left corners of plots in the first column of the array of plots.