(a) Modified radial Hough functions w_νkm(a, θ) (normalised) for three different modes (with specified spin parameter ν). Colour conventions are the same as those in Fig. 3. (b) Eigenvalue Λ_νkm(a) profiles corresponding to the eigenfunctions in (a). Points indicated with a ⋆ correspond to eigenvalues obtained by solving the GLTE. Red points were found via quadratic interpolation. The considered number of collocation points was N = 200.