Fig. 2
Periodograms and peaks of IEA rhythms. a Average periodograms across all subjects (N = 37) showing ultradian, circadian, and multidien peaks. For better visualization, unsupervised clustering across all subjects revealed three patterns: (i) about weekly-to-biweekly rhythm (peaks at 7.5 and 15 days, N = 9), (ii) about tri-weekly rhythm (peak at 20 days, N = 12), and (iii) about monthly rhythm (peak at 26 days, N = 16). Shading indicates ± 1 SD. b Histograms showing the number of subjects with a peak in the periodogram at a given period. The distributions are similar (p = 0.87, χ2-test) in male (N = 22) and female (N = 15) subjects
