  We review one of complementary methods for time series analysis - the method
of "Running Sines". "Crash tests" of the method include signals with a large
period variation and with a large trend. The method is most effective for
"nearly periodic" signals, which exhibit "wavy shape" with a "cycle length"
varying within few dozen per cent (i.e. oscillations of low coherence). This is
a typical case for brightness variations of long-period pulsating variables and
resembles QPO (Quasi-Periodic Oscillations) and TPO (Transient Periodic
Oscillations) in interacting binary stars - cataclysmic variables, symbiotic
variables, low-mass X-Ray binaries etc. General theory of "running
approximations" was described by Andronov (1997A &AS..125..207A), one of
realizations of which is the method of "running sines". The method is related
to Morlet-type wavelet analysis improved for irregularly spaced data (Andronov,
1998KFNT...14..490A, 1999sss..conf...57A), as well as to a classical "running
mean" (="moving average"). The method is illustrated by an application to a
model signal with strongly variable period, as well as to a semi-regular
variable AF Cyg. Some other stars studied with this method are discussed, e.g.
RU And (switching between "Mira-type" large amplitude oscillations and time
intervals of "constancy"), intermediate polars MU Cam (1RXS J062518.2+733433)
and BG CMi, magnetic dwarf nova DO Dra, symbiotic stars UV Aur and V1329 Cyg.
