estimates were averaged to provide smooth spectra.
analyses were performed on 10-day intervals on the whole actogram.
and Krzan, G.: 2016, Analysis of PCC model dependent periodic signals in GLONASS position time series using Lomb-Scargle periodogram
. Acta Geodyn.
In this way, we note in Figure 3 that the harmonics of higher intensity (I) corresponds to the cycle (1/[f.sub.i]) of 6 and 12 months, given that the periodogram
shows that this time series contains two cosine-sine peaks at these frequencies.
From the filtered R-R signals, periodogram
is calculated using the Lomb-Scargle algorithm , The Lomb-Scargle algorithm allows efficient computation of a Fourier-like power spectrum estimator from unequally spaced data (as are the R-R intervals).
Step 3: The modified periodogram
value is formed for each segment using a discrete Fourier transform.
Significant periods were detected using two different periodogram
analyses, chi-square and Lomb-Scargle.
. This is the most basic nonparametric method based on the calculation of the Fourier Transform.
The frequency content of the slow and fast components in the ML and AP directions were estimated by the Fourier analysis of the characteristics of the power spectral density using Welch's periodogram
In this method, we first computed the PSD based on Welch Periodogram
: a hamming window of 400 points was used with a 50% overlap between adjacent windowed sections.
As concerning the nonparametric approaches, we have considered the frequency domain decomposition (FDD) , periodogram
, and Welch estimation  methods.
The mostly common tool for periodicity analysis of both evenly and unevenly sampled signals is the Periodogram
method, which is an estimator of the signal energy in the frequency domain by Deeming (1975) .