Single parameter representation for the SCAN (upper panel) and M11-L (lower panel) meta-GGA exchange functionals as a 3D function (left plots) of the reduced density variables \(u\), eq. \ref{eqn:4}, and the local kinetic energy density variable \(w\), eq. \ref{eqn:7}. The right plots represent slices at constant \(u=0\). For both functionals, the black dots are the decoded points, the orange solid curve is the original enhancement factor as obtained directly from LibXC, and the dashed red curve is the result of the decoding of the single parameter and the interpolation via univariate cubic spline. Results are obtained on a grid of  \(20\times20\)  points and \(\beta=12\). A Jupyter notebook to encode every meta-GGA exchange functional in LibXC, as well as to reproduce the plots and to calculate the encoding and interpolation errors is associated with the Figure.