First eigenvalue compared to epoch folding for PSR B0833- 45. The top panel shows the χ² optimization and the bottom panel the first PC eigenvalue for a waterfall with M = 20 number of divisions. Similarly as in Fig. 9, the noise level is higher in the first PC. The optimum peaks are close, and their difference is ∆P = |P_PCA − Pχ²| = 120 ns. Both sets were started with the same initial conditions, ∆s = 10 ns, ∆t = 2.793 ms, number of iterations, and initial trial period.