Left panel: eigenvalues of the inversion matrix (Eq. (11)), plotted as a function of the increasing position index, as obtained for a set of 448 artificial splittings with l = 1 − 6. Different colours indicate similar solutions obtained for the system of linear equations inverted. Right panel: histogram of the degeneracy of the eigenvalues, i.e. the number of times a similar number appears in the vector of eigenvalues.