Good article was published -
Practical evaluation of the adaptive market following method
The trading strategy presented in this article was first described by Vladimir Kravchuk in the "Currency speculator" magazine in 2001 - 2002. The system is based on the use of digital filters and spectral estimation of discrete time series.
A live chart of quote changes may have an arbitrary form. In mathematics, such functions are called non-analytic. The famous Fourier theorem implies that any function on a finite time interval can be represented as an infinite sum of sinusoidal functions. Consequently, any time signals can be uniquely represented by frequency functions, which are called their frequency spectra.
For non-random signals, the transition from the time-domain to frequency-domain representation (i.e., calculation of the frequency spectrum) is performed using the Fourier transform. Random processes are represented by the process' power spectral density (PSD), which is a Fourier transform not of the random process itself, but that of its autocorrelation function.