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There are two computationally distinct methods
by which we can
compute a spectrum: (1) compute all the *s*_{k} coefficients
from (37) and
then form the cosine sum (41) for each ; and
alternately, (2) evaluate *B*(*Z*) for some value of Z on the unit circle,
and multiply the resulting number by its complex conjugate.
Repeat for many values of *Z* on the unit circle.
When there are more than about twenty lags,
method (2) is cheaper, because
the fast Fourier transform discussed in chapter can be used.

** Next:** Common signals
** Up:** CORRELATION AND SPECTRA
** Previous:** Spectra in terms of
Stanford Exploration Project

10/21/1998