CODEWITHSUNDEEP
python-3.xnumpystatisticsfftastropy
Andreas Ioannou
Andreas Ioannou

Reputation: 43

Lomb Scargle phase

Is there any way I can extract the phase from the Lomb Scargle periodogram? I'm using the LombScargle implementation from gatspy.

from gatspy.periodic import LombScargleFast

model = LombScargleFast().fit(t, y)
periods, power = model.periodogram_auto()
frequencies = 1 / periods
fig, ax = plt.subplots()
ax.plot(frequencies, power)
plt.show()

Power gives me an absolute value. Any way I can extract the phase for each frequency as I can for a discrete fourier transform.

Upvotes: 3

Views: 1242

Answers (2)

Ranjan Kumar Sahu
Ranjan Kumar Sahu

Reputation: 73

let's consider that you're looking for a specific frequency fo. Then the corresponding period can be given by P = 1/fo. We can define a function, as in below:

def phase_plot(t,period):
    #t is the array of timesteps
    phases = (time/period)%1.

this will give you all the phases for that particular frequency of interest.

Upvotes: 0

mdurant
mdurant

Reputation: 28683

The Lomb-Scargle method produces a periodogram, i.e., powers at each frequency. This is in order to be able to be performant, compared to directly least-squares fitting a sinusoidal model. I don't know about gatspy, but astropy does allow you to compute the best phase for a specific frequency of interest, see http://docs.astropy.org/en/stable/stats/lombscargle.html#the-lomb-scargle-model . I imagine doing this for many frequencies is many times slower than computing the periodogram.

-EDIT-

The docs outline moved to: https://docs.astropy.org/en/stable/timeseries/lombscargle.html

Upvotes: 2

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