The LNP_TEST function computes the Lomb Normalized Periodogram
of two sample populations X and Y and tests the hypothesis that
the populations represent a significant periodic signal against
the hypothesis that they represent random noise. LNP_TEST is
based on the routine fasper described in section 13.8 of
Numerical Recipes in C: The Art of Scientific Computing (Second
Edition), published by Cambridge University Press, and is used
by permission. Result = LNP_TEST( X, Y [, /DOUBLE] [,
HIFAC=scale_factor] [, JMAX=variable] [, OFAC=value] [,
WK1=variable] [, WK2=variable] ) The result is a two-element
vector containing the maximum peak in the Lomb Normalized
Periodogram and its significance. The significance is a value in
the interval [0.0, 1.0]; a small value indicates that a
significant periodic signal is present. An n-element integer,
single-, or double-precision floating-point vector containing
equally or unequally spaced time samples. An n-element integer,
single-, or double-precision floating-point vector