Review and classification of variability analysis techniques with clinical applications

Table 6 Summary of the energetic domain

Domain Assumptions	Features	Feature Assumptions	Transformation used	References
The information is held in the energy of the signal	Frequency features	Stationarity of the time series	Frequency transformations	[9, 18, 22, 25, 60, 61, 75]
	Time-frequency features		Time-frequency transformations	[9, 18, 22, 25, 60, 61, 75]
	Energy operators	The time series expresses periodicity		[73, 74]
	Multiscale time irreversibility	The time series is created from a dissipative process, which dissipation can be quantified by the degree of temporal asymmetry		[76]

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