. 2021 Jun 24;21(13):4315. doi: 10.3390/s21134315

Table 2.

Summary of feature extraction in normal and imputed conditions. The variable $n_{x}$ denotes the sample position.

Feature	Definition	Normal Condition	Imputed Condition
Systolic peak $(n_{s y s .})$	PPG peak in systole	$n_{Z C ↓}^{(1)}$ in systole with the largest	1. $n_{m i n (l a s t) < n_{e}}^{(1)}$ if $n_{m i n (l a s t) < n_{e}}^{(1)} \in [n_{d}, n_{e}]$
		PPG amplitude	2. $n_{d}$
Notch $(n_{n o t c h})$	PPG local minimum around	$n_{Z C ↑}^{(1)}$	1. Same as imputed systolic peak 1.
	systole boundary		or imputed diastolic peak 1.
			2. $n_{e}$
Diastolic peak $(n_{d i a .})$	PPG peak in diastole	first $n_{Z C ↓}^{(1)}$ in diastole	1. $n_{m a x (1) > n_{e}}^{(1)}$ if $n_{m a x (1) > n_{e}}^{(1)} \in [n_{e}, n_{f}]$
			2. $n_{f}$
Maximal slope $(n_{m s})$	First local maximum in FDPPG	First $n_{Z C ↓}^{(2)}$	$n_{m i n (1)}^{(2)}$
Point a $(n_{a})$	First local maximum in SDPPG	First $n_{Z C ↓}^{(3)}$	-
Point b $(n_{b})$	First local minimum in SDPPG	First $n_{Z C ↑}^{(3)}$	$n_{m a x (2)}^{(3)}$
Point c $(n_{c})$	Last local maximum in SDPPG	Last $n_{Z C ↓}^{(3)} \in [n_{a}, n_{e}]$	1. $n_{m a x (2)}^{(3)}$ if degeneration of b and c1
	before $n_{e}$		2. $n_{m i n (2)}^{(3)}$ if degeneration of c1 and d1
			3. $n_{m a x (3)}^{(3)}$ if degeneration of d1 and c2
			4. $n_{m i n (3)}^{(3)}$ if degeneration of c2 and d2
Point d $(n_{d})$	Last local minimum in SDPPG	Last $n_{Z C ↑}^{(3)} \in [n_{a}, n_{e}]$	1. $n_{m i n (2)}^{(3)}$ if degeneration of c1 and d1
	before $n_{e}$		2. $n_{m a x (3)}^{(3)}$ if degeneration of d1 and c2
			3. $n_{m i n (3)}^{(3)}$ if degeneration of c2 and d2
Point e $(n_{e})$	Local maximum in SDPPG	$n_{Z C ↓}^{(3)} \in [\frac{0.16}{T_{s}} + 0.1 N, \frac{0.3}{T_{s}} + 0.1 N]$	-
	around end-systolic boundary
Point f $(n_{f})$	First local minimum in SDPPG	First $n_{Z C ↑}^{(3)}$ after $n_{e}$	-
	after $n_{e}$