My friend Steve Dean who runs the NY meetup for Quantified Self, sent another friends wavelet coherence chart (will get his permission to use his name here) for Heart Rate Variability as measured during a yoga session with another person's HRV during the same session. The wavelet chart captures correlation of frequency over time....the blobby parts (circled) show when they started to synch up heart rate after about an hour. And btw, heart rate variability is a good one. Worth knowing more about. But for this post, I'm all over MatLabs Wavelet Coherence charts.