Table 1.

Features extracted in time domain and frequency domain.

Domain	Feature	Formula
Time	Mean value (Tmv)	$T_{mv}={\displaystyle {\sum }_{i=1}^n{x}_i/n}$
	Maximum (Tmax)	$T_{\max }=\max (x_i)$
	Root mean square (Trms)	$T_{rms}=\sqrt{{\displaystyle {\sum }_{i=1}^n{x}_i^2/n}}$
	Variance (Tvr)	$T_{vr}=\frac{{\displaystyle {\sum }_{i=1}^n{(x_i-T_{mv})}^2}}{n-1}$
	Standard Deviation (Tsd)	$T_{sd}=\sqrt{T_{vr}}$
	Peak-to-peak (Tp2p)	$T_{p2p}=T_{\max }-\min (x_i)$
	Waveform Factor (Twf)	$T_{wf}=n·T_{rms}/({\displaystyle {\sum }_i^n\left|x_i\right|})$
	Skewness Factor (Tsf)	$T_{sf}=\frac{{\displaystyle {\sum }_{i=1}^n{(x_i-T_{mv})}^3}}{n·T_{sd}^3}$
	Kurtosis Factor (Tkf)	$T_{kf}=\frac{{\displaystyle {\sum }_{i=1}^n{(x_i-T_{mv})}^4}}{n·T_{sd}^4}-3$
	Crest Factor (Tcf)	$F_{cf}=\max (\left|x_i\right|)/T_{rms}$
Frequency	Mean of power spectrum (Fmv)	$F_{mv}={\displaystyle {\sum }_{i=1}^n{S}_i}/n$
	Maximum of power spectrum (Fmax)	$F_{\max }=\max (S_i)$
	Root mean square of power spectrum (Frms)	$F_{rms}=\sqrt{{\displaystyle {\sum }_{i=1}^n{S}_i^2/n}}$
	Variance of power spectrum (Fvr)	$F_{vr}=\frac{{\displaystyle {\sum }_{i=1}^n{(S_i-F_{mv})}^2}}{n-1}$
	Skewness of power spectrum (Fsf)	$F_{sf}=\frac{1}{n}\frac{{\displaystyle {\sum }_{i=1}^n{(S_i-F_{mv})}^3}}{F_{vr}^{3/2}}$
	Kurtosis of power spectrum (Fkf)	$F_{kf}=\frac{1}{n}\frac{{\displaystyle {\sum }_{i=1}^n{(S_i-F_{mv})}^3}}{F_{vr}^2}$
	Relative spectral peak per band (Frs)	$F_{rs}=\frac{F_{\max }}{F_{mv}}$