Table 2 Feature definition

Mean Absolute Value

$\mathit{M}\mathit{A}{\mathit{V}}_{\mathit{i}}=\frac{\mathbf{1}}{\mathit{N}}{\displaystyle \sum _{\mathit{k}\mathbf{=}\mathbf{1}}^{\mathit{N}}}\left|{\mathit{x}}_{\mathit{k}}\right|$

Root Mean Square

$\mathit{R}\mathit{M}{\mathit{S}}_{\mathit{i}}=\sqrt{\frac{\mathbf{1}}{\mathit{N}}}{\displaystyle \sum _{\mathit{k}\mathbf{=}\mathbf{1}}^{\mathit{N}}}{\mathit{x}}_{\mathit{k}}^{\mathbf{2}}$

Waveform Length

$\mathit{W}{\mathit{L}}_{\mathit{i}}={\displaystyle \sum _{\mathit{k}\mathbf{=}\mathbf{1}}^{\mathit{N}}}\left|{\mathit{x}}_{\mathit{k}}\mathbf{-}{\mathit{x}}_{\mathit{k}\mathbf{-}\mathbf{1}}\right|$

Willison Amplitude

$\mathit{W}\mathit{A}\mathit{M}{\mathit{P}}_{\mathit{i}}={\displaystyle \sum _{\mathit{k}=\mathbf{1}}^{\mathit{N}-\mathbf{1}}}\mathit{f}\left(\left|{\mathit{x}}_{\mathit{k}}-{\mathit{x}}_{\mathit{k}\mathbf{+}\mathbf{1}}\right|\right)$

$\mathit{f}\left(\mathit{x}\right)=\left\{\begin{array}{c}\hfill \mathbf{1}\mathit{x}>{\mathit{x}}_{\mathit{t}\mathit{h}}\hfill \\ \hfill \mathbf{0}\mathit{otherwise}\hfill \end{array}\right\}$

Zero Crossings

${\mathit{f}}_{\mathit{k}}=\left\{\begin{array}{c}\hfill \mathbf{1}{\mathit{x}}_{\mathit{k}}{\mathit{x}}_{\mathit{k}\mathbf{+}\mathbf{1}}<\mathbf{0}\hfill \\ \hfill \mathbf{0}\mathit{otherwise}\hfill \end{array}\right\}$

$\mathit{Z}{\mathit{C}}_{\mathit{i}}={\displaystyle \sum _{\mathit{k}=\mathbf{1}}^{\mathit{N}-\mathbf{1}}}{\mathit{f}}_{\mathit{k}}$

Autoregressive Model (AR)

${\mathit{y}}_{\mathit{n}}=-{\displaystyle \sum _{\mathit{k}=\mathbf{1}}^{\mathit{p}}}{\mathit{a}}_{\mathit{k}}{\mathit{x}}_{\mathit{n}-\mathit{k}}+{\mathit{w}}_{\mathit{n}}$

In this study, p = 6.

Power Spectral Density

$\mathit{P}\mathit{S}\mathit{D}\left(\mathit{f}\right)=\frac{\mathbf{1}}{\mathit{N}}\left|{\displaystyle \sum _{\mathit{k}=\mathbf{0}}^{\mathit{N}}}{\mathit{x}}_{\mathit{k}}{\mathit{e}}^{-\mathit{j}\mathbf{2}\mathit{\pi }\mathit{f}}\right|$

Power Spectral Density Averages

$\mathit{P}\mathit{S}\mathit{D}\_\mathit{A}{\mathit{v}}_{\mathit{i}}=\frac{\mathbf{1}}{{\mathit{f}}_{\mathit{k}}-{\mathit{f}}_{\mathit{k}-\mathbf{1}}}{\displaystyle {\int }_{{\mathit{f}}_{\mathit{k}}}^{{\mathit{f}}_{\mathit{k}-\mathbf{1}}}\mathit{P}\mathit{S}\mathit{D}}\left(\mathit{f}\right)\mathit{d}\mathit{f}$

Power Spectral Density Moments

$\mathit{P}\mathit{S}\mathit{D}\_\mathit{M}{\mathit{o}}_{\mathit{i}\mathit{y}}={\displaystyle {\int }_{\mathbf{0}}^{\mathit{w}}{\mathit{f}}^{\mathit{y}}}\mathit{P}\mathit{S}\mathit{D}\left(\mathit{f}\right)\mathit{d}\mathit{f}$

In this study, w = 250 Hz and y = 1,2,3