# Table 3 Equations and descriptions of peak features

Peak feature Feature name Equation Description
Amplitudes Peak-to-peak amplitude of the first half wave $$f_{1} = \left| {x\left( {PP_{i} } \right) - x\left( {VP1_{i} } \right)} \right|$$ Amplitude between the magnitude of peak and the magnitude of valley at the first half wave
Peak-to-peak amplitude of the second half wave $$f_{2} = \left| {x\left( {PP_{i} } \right) - x\left( {VP2_{i} } \right)} \right|$$ Amplitude between the magnitude of peak and the magnitude of valley of the second half wave
Turning point amplitude of the first half wave $$f_{3} = \left| {x\left( {PP_{i} } \right) - x\left( {TP1_{i} } \right)} \right|$$ Amplitude between the magnitude of peak and the magnitude of turning point at the first half wave
Turning point amplitude at the second half wave $$f_{4} = \left| {x\left( {PP_{i} } \right) - x\left( {TP2_{i} } \right)} \right|$$ Amplitude between the magnitude of peak and the magnitude of turning point at the second half wave
Moving average amplitude $$f_{5} = \left| {x\left( {PP_{i} } \right) - MAC\left( {PP_{i} } \right)} \right|$$ Amplitude between the magnitude of peak and the magnitude of moving average
Widths Peak width $$f_{6} = \left| {VP1_{i} - VP2_{i} } \right|$$ Width between valley point of first half point and valley point at second half wave
First half wave width $$f_{7} = \left| {PP_{i} - VP1_{i} } \right|$$ Width between peak point and valley point at first half wave
Second half wave width $$f_{8} = \left| {PP_{i} - VP2_{i} } \right|$$ Width between peak point and valley point of second half wave
Turning point width $$f_{9} = \left| {TP1_{i} - TP2_{i} } \right|$$ Width between turning point at first half wave and turning point at the second half wave
First half wave turning point width $$f_{10} = \left| {PP_{i} - TP1_{i} } \right|$$ Width between turning point at first half wave and peak point
Second half wave Turning point width $$f_{11} = \left| {PP_{i} - TP2_{i} } \right|$$ Width between turning point at second half wave and peak point
FWHM $$f_{12} = \left| {HP1_{i} - HP2_{i} } \right|$$ Width between half point of first half wave and half point of second half wave
Slopes Peak slope at the first half wave $$f_{13} = \left| {\frac{{x\left( {PP_{i} } \right) - x\left( {VP1_{i} } \right)}}{{PP_{i} - VP1_{i} }}} \right|$$ Slope between a peak point and valley point at the first half wave
Peak slope at the second half wave $$f_{14} = \left| {\frac{{x\left( {PP_{i} } \right) - x\left( {VP2_{i} } \right)}}{{PP_{i} - VP2_{i} }}} \right|$$ Slope between a peak point and valley point at the second half wave
Turning point slope at the first half wave $$f_{15} = \left| {\frac{{x\left( {PP_{i} } \right) - x\left( {TP1_{i} } \right)}}{{PP_{i} - TP1_{i} }}} \right|$$ The slope between peak point and turning point at the first half wave
Turning point slope at the second half wave $$f_{16} = \left| {\frac{{x\left( {PP_{i} } \right) - x\left( {TP2_{i} } \right)}}{{PP_{i} - TP2_{i} }}} \right|$$ The slope between peak point and turning point at the second half wave