First eigenvalue compared to epoch folding for PSR B0540-69. The top panel shows the χ² optimization and the bottom panel the first PC eigenvalue for a waterfall with M = 20 number of divisions. The eigenvalue, λ_ℓ,1 presents a noisier signal, i.e., a lower signal-to-noise ratio. However, the maximum from each plot reaches a similar result within less than 10 ns. The periods, P_x2 and P_PCA, were determined by a least-squares fit and adjusting a Gaussian (red line). The center of the Gaussian is the reported period, and the errors are 4.34 ns and 8.60 ns. The FWHM of the Gaussian is also reported. Both sets were started with the same initial conditions, ∆_s = 10 ns, ∆t = 1 ms, number of iterations, and initial trial period.