The PPG signal in (a) is shown: (b) transformed into a 3D attractor in phase space; and (c) transformed into a 2D attractor using symmetric projection attractor reconstruction, with (d) showing the corresponding density plot of this 2D attractor.
Figure created using data from the PPG Diary Study (at https://doi.org/10.5281/zenodo.3268500 ).
Own work
Peterhcharlton