Correlations between DIBs λ8621 and λ8648 for 179 selected measurements for (a) fit and integrated EW₈₆₄₈ outside the masked region between 8660 and 8668 Å; (b) fit EW; (c) measured central wavelength; and (d) FWHM. The dashed green line in panel a traces the one-to-one correspondence. The colored points in panel b are the results from GFPR. The color in panel c represents the number density estimated by the Gaussian KDE, and the red line is a linear fit to all the data points. The Pearson coefficient (r_p) of the correlation between the parameters of λ8621 and λ8648 for the 179 selected measurements is indicated in panels b and c.