# Nyquist Frequency on semi-unevenly sampled data

I have a data set that has 'kind of' constant sampling rate - it switches between 1 min and 2 min. About 70% of the times, samples are taken every 1 minute, and about 30%, samples are taken every 2 minutes.

I tried using FFT, but it didn't work because samples aren't evenly spaced. Instead I applied Lomb-Scargle transformation, and obtained a good looking plot. Upper plot is a Lomb-Scargle periodogram, and lower plot is the original sample data with varying sampling rate (1 min or 2 min).

What should I use for Nyquist Frequency in this case?

your plots show symmetry around a “center” frequency which is the same as what a FFT does for real inputs, except a FFT would not extend to start a third interval. The high half frequencies(above $$\approx$$ .017 to .033) are the negative frequencies in FFT speak. you can ignore them when you have a real signal.