In the following plot of respiration during meditation, we see a regular repetition of inhalations and exhalations with a wave-like quality.
Selecting a range of cycles, we can average the values centered around the peaks to extract a waveform that represents the entire range. Averaging over 12 cycles, we get the following:
An interesting aspect of this waveform is that the exhalations are almost twice as long as the inhalations. Here, one complete cycle is 19 seconds long which corresponds to 3.2 breaths/minute. Compare this with the waveform for reading: