Amplitude of each waterfall-PCA folding merit function,ξ_ℓ (M3)(color map rows). Top panel: average of all M values, 3 ≤ M ≤ 20, and it is then plotted as a solid line. A scatter plot of the original data is overplotted (with the same amplitude color bar). There is a clear noise reduction in the 〈ξ_ℓ〉 _M computed with Eq. (4). The case corresponds to the nominal Vela pulsar of 5.5 million counts. The solid line has a CP_ξ = 8.9 (Table 2). Some discrete merit functions (rows in the color map) are plotted in Fig. 17.