The BAOlet function. Here we show a two-dimensional (2D) plot (bottom) of the wavelet ψ_R,s(x) used in the analysis, as defined by Eq. (1). The top panel shows a 1D slice along the dashed-dotted axis. The wavelet is plotted here for R = 105   h^-1   Mpc, s = 30   h^-1   Mpc. The red dot marks the centre of the wavelet. This function has a null mean (provided that R > 2s), and compact support. It takes non-zero values only for R − 2s ≤ |x| ≤ R + 2s.