11.14.1. astroML_addons.periodogram.lomb_scargle

astroML_addons.periodogram.lomb_scargle()

(Generalized) Lomb-Scargle Periodogram with Floating Mean

Parameters :

t : array_like

sequence of times

y : array_like

sequence of observations

dy : array_like

sequence of observational errors

omega : array_like

frequencies at which to evaluate p(omega)

generalized : bool

if True (default) use generalized lomb-scargle method otherwise, use classic lomb-scargle.

subtract_mean : bool

if True (default) subtract the sample mean from the data before computing the periodogram. Only referenced if generalized is False.

significance : None or float or ndarray

if specified, then this is a list of significances to compute for the results.

Returns :

p : array_like

Lomb-Scargle power associated with each frequency omega

z : array_like

if significance is specified, this gives the levels corresponding to the desired significance (using the Scargle 1982 formalism)

Notes

The algorithm is based on reference [R24]. The result for generalized=False is given by equation 4 of this work, while the result for generalized=True is given by equation 20.

Note that the normalization used in this reference is different from that used in other places in the literature (e.g. [R25]). For a discussion of normalization and false-alarm probability, see [R24].

To recover the normalization used in Scargle [R26], the results should be multiplied by (N - 1) / 2 where N is the number of data points.

References

[R24]

(1, 2, 3) Zechmeister and M. Kurster, A&A 496, 577-584 (2009)

[R25]

(1, 2) Press et al, Numerical Recipies in C (2002)

[R26]

(1, 2) Scargle, J.D. 1982, ApJ 263:835-853