
186 Practical Biomedical Signal Analysis Using MATLAB
R
(Sect. 2.4.1). In Figure 4.34, the first four components, difference between compo-
nent one and four, and Hilbert amplitude ratio of third and first component (a3/a1) as
a function of time are illustrated. The value of component ratio may be considered as
a convenient measure of the HRV rhythms evolution. One can observe the increase
of the ratio a3/a1 after changing posture.
FIGURE 4.35: Instantaneous frequency as a function of time for the first four
components presented in Figure 4.34. From [Echeverria et al., 2001].
In Figure 4.35 instantaneous frequency as a function of time for first components ...