Fourier series of periodic functions with variable period and evaluation of the variable period for determination of heart rhythm variability
The article draws attention to the fact that in addition to periodic empirical signals, whose model is a periodic function, there are signals that behave like periodic, but the period of their values repetition is no longer constant and changes in some way. An illustrative example is electrocardiograms (ECGs) obtained during or after an impact of some “exciter of calm”, for example, physical exertion, on the patient. How to study periodic signals with a variable period (PSVP)?