Coefficients of variations (CVs), calculated as the standard deviations divided by the mean values, within the |$2R$| circular regions of the |$I_{\rm {PAH}}/I_{\rm {TIR}}$| maps after removing the radial profile (figure 7), plotted against the Galactocentric distance. The data points are color-coded according to the CF obtained in Hanaoka et al. (2019) (the color will be discussed in section 4). (Color online)