Correlations of low-, mid- and high-frequency CPX levels with the 3D texture principal components. The lower triangle depicts the individual scatter plots, the upper triangle the coefficient of determination of the respective linear regression. The parameter names in the diagonal denote the variables on the axes of the matrix elements, e.g. the lowest row depicts the individual scatter plots of mid, high, and PC1 to PC3 variables on the abscissa vs. the low-frequency component on the ordinate. In addition, the diagonal elements also show the variables’ kernel density estimate.