Figure 3: A comparison of raw and filtered photoplethysmogram (PPG) waveforms in G1, G2, and G3 classes.
From: An optimal filter for short photoplethysmogram signals
The skewness signal quality index values are shown for the raw PPG waveform (black color), the 4th-order Cheby II (red color), and 4th-order Butterworth (blue color) filters.
