GLOSSARY OF
TERMS
USED
IN
TIME SERIES
ANALYSIS
OF CARDIOVASCULAR
DATA
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POWER
Time average of time-series energy
If x(k) is the k-th value of a time series of N
samples with sampling period 
,
its energy E is defined as:
When the series x(k) is produced by a stationary stochastic
process of infinite duration rather than by a deterministic waveform of
finite duration, the energy is usually infinite, and the quantity of interest
is the power P defined as the energy per unit of time:
Note that the units of power are not the units of physical power, being
the square of the units of the time series, e.g. mmHg2 for blood
pressure time series, ms2 for interval tachogram. For zero-mean
time series, the power is equal to the variance of the sample of the N
values x(k).
Kay SM, Marple SL Jr. (1981) Spectrum Analysis - A
Modern Perspective. Proceeding of the IEEE, vol.69 (11), 1380-1419
(PC 07-09-1999)
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