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Table 1 Summary of quantities used in recurrence quantification analysis. Modified after Webber and Zbilut (2005): https://www.nsf.gov/pubs/2005/nsf05057/nmbs/nmbs.pdf

From: Nonlinear dynamical analysis of GNSS data: quantification, precursors and synchronisation

%recurrence, %REC

Percentage of recurrent points falling within the specified radius, ε.

\( \%\mathrm{REC}=100\frac{number\ of\ points\ in\ triangle}{\varepsilon \left(\varepsilon -1\right)/2} \)

%determinism, %DET

Percentage of recurrent points forming diagonal line structures. This is a measure of determinism in the signal.

\( \%\mathrm{DET}=100\frac{number\ of\ points\ in\ diagonal\ lines}{number\ of\ recurrent\ points} \)

Linemax, DMAX

The length of the longest diagonal line in the plot (except main diagonal).

DMAX = length of longest diagonal line in the recurrence plot

Entropy, ENT

The Shannon information entropy of all diagonal line lengths over integer bins in a histogram. This is a measure of signal complexity with units bits/bin.

ENT =  −  ∑ (Pbin)log2(Pbin)

Trend. TND

A measure of system stationarity.

\( \mathrm{TND}=1000\left(\begin{array}{l} slope\ of\% local\ recurrence\ \\ {}\kern2.25em vs. displacement\end{array}\right) \)

%laminarity, %LAM

The percentage of recurrent points forming vertical line structures.

\( \%\mathrm{LAM}=100\frac{number\ of\ points\ in\ vertical\ lines}{number\ of\ recurrent\ points} \)

VMAX

The length of the longest vertical line in the plot.

VMAX = length of longest vertical line in the recurrence plot

Trapping time, TT

The average length of vertical line structures.

TT = Average length of vertical lines ≥ parameter line