Table 4.

Features extracted only from the systolic and diastolic silent intervals (tagged as m1 and m2, respectively).

Index	Tag	Description
Envelope approximation using 2nd order polynomial coefficients:
49	a0	constant term of the polynomial
50	a1	linear term of the polynomial
51	a2	quadratic term of the polynomial
Energy distributed across time (4 quarters):
52	en_1/4	1st quarter energy
53	en_2/4	2nd quarter energy
54	en_3/4	3rd quarter energy
55	en_4/4	4th quarter energy
Statistics:
56	mean	mean value
57	std	standard deviation
Statistics distributed across time (4 quarters):
58	mean_1/4	1st part mean
59	mean_2/4	2nd part mean
60	mean_3/4	3rd part mean
61	mean_4/4	4th part mean
62	std_1/4	1st part standard deviation
63	std_2/4	2nd part standard deviation
64	std_3/4	3rd part standard deviation
65	std_4/4	4th part standard deviation
Structural:
66	frq_zero	number of zeros per second
67	skewness	relative position of the maximum absolute value of the signal around the middle point of the interval.