TABLE 4.

Summary of the definition of the dynamic features. All the listed ML features can also be computed for the AP axis. For units, cm stands for centimeter, s for seconds, Hz for Hertz, and − for unitless. *: This feature is obtained by summing non‐homogeneous term, and therefore has no valid units

Feature	Full name	Formula	Units
SWAY LENGTH ML	Sway length ML	${\sum }_n|X_{n+1}‐X_n|$
SWAY LENGTH	Total sway length	${\sum }_n\sqrt{{\left(X_{n+1}‐X_n\right)}^2+{\left(Y_{n+1}‐Y_n\right)}^2}$	cm
MEAN SPD ML	Average velocity ML	SWAY LENGTH ML/T	cm.s‐1
MEAN SPD	Average velocity	SWAY LENGTH/T	cm.s‐1
AREA PER SEC.	Sway area per sec.	$\frac{1}{2\mathrm{T}}{\sum }_n\left|X_{n+1}{Y}_n‐X_n{Y}_{n+1}\right|$	cm².s‐1
STD SPD ML.	Deviation velocity ML	$\sqrt{\frac{1}{\mathrm{N}}{\sum }_n{\left(V_n^x‐\overline{V^x}\right)}^2}$	cm.s‐1
STD SPD.	Deviation velocity	$\sqrt{\frac{1}{\mathrm{N}}{\sum }_n{\left(V_n‐\overline{V}\right)}^2}$	cm.s‐1
PHASE PLANE ML	ML phase plane parameter	$\sqrt{\text{RMS}{\text{ML}}^2+\text{STD}\text{SPD}{\text{ML}}^2}$	*
VFY	—	$\text{STD}{\text{SPD}}^2/\text{MEAN}\text{AP}$	cm.s‐ 2
LFS	Length over area	$\frac{\text{SWAY}\text{LENGTH}}{95\%\text{CONF}.\text{AREA}}$	cm
FRACTAL DIM	Fractal dimension	See Def. Fractal Dimension	—
SET OF ZERO CROSS. ML	Set of zero‐crossings ML	$Z^{V^x}$
ZERO CROSS. ML	Number of zero‐crossings ML	$\#Z^{V^x}$
PEAK VEL. + ML	Mean positive peak of ML Vel.	see Def.	cm.s‐1
PEAK VEL. ‐ ML	Mean negative peak of ML Vel.	see Def.	cm.s‐1
PEAK VEL. ML	Mean peak of ML velocity	$\frac{1}{K}{\mathrm{\Sigma }}_{\ell }{p}_{\ell }^{V^x}$	cm.s‐1
PEAK SD	Mean peak of sway density	$\frac{1}{K}{\mathrm{\Sigma }}_{\ell }{p}_{\ell }^{\text{SD}}$	s
DIST. PEAK SD	Mean spatial dist. between S.D. peaks	See Def	cm
MEAN FREQ. ML	Mean frequency ML	$\frac{1}{4\sqrt{2}}\times \frac{\text{MEAN}\text{SPD}\text{ML}}{\text{MEAN}\text{DIST}\text{ML}}$	Hz
MEAN FREQ. ML‐AP	Mean frequency	$\frac{1}{4\sqrt{2}}\times \frac{\text{MEAN}\text{SPD}}{\text{MEAN}\text{DIST}}$	Hz