A graphical plot with abscissa given by the number 
of consecutive numbers constituting
a single period and ordinate given by the correlation
ratio 
.
The equation of the periodogram is
 |
where each of the terms of the sequence 
consists of a simple periodic part of period 
, together with a part which does not involve this periodicity
, so
 |
is the standard deviation of the
s, 
is the standard deviation of the 
s, and 
is the number of periods covered by the observations.
