Table 2. Feature set extracted based on previous studies.

Name	Derived from		Details
	RRa	Amplb
RMSSD	×		Square root of the average of the squared difference between adjacent RR intervals.
SDNN	×		Standard deviation of the difference between adjacent RR intervals.
NN50	×		Number of adjacent RR intervals exceeds 50 ms.
pNN50	×		NN50 divides by the number of RR intervals.
Mean RR	×		Mean of RR intervals.
Mean HR	×		Mean of heart rate (HR), which is derived from RR intervals.
Normalized VLF	×	×	Normalized very low frequency (VLF) component of the corresponding signal.
Normalized LF	×	×	Normalized Low frequency (LF) component of the corresponding signal.
Normalized HF	×	×	Normalized high frequency (HF) component of the corresponding signal.
LF/HF	×	×	The ratio of LF to HF of the corresponding signal.
LF/(LF + HF)	×	×	The ratio of LF to LF+HF of the corresponding signal.
HF/(LF + HF)	×	×	The ratio of HF to LF+HF of the corresponding signal.

Notes.

^aRR intervals of single-lead ECG signal.

^bAmplitudes of single-lead ECG signal.