Fig. 4
Illustration of smoothing using the convex envelope and shows the actual graphics provided by PeakCaller. In the upper graph, for the original Ca2+ recording (in black), the smoothing using a convex envelope is given by the dotted red curve. The lower graph shows the de-trended data series, which is simply the quotient of the original data divided by the smoothed data. Note in this case that the de-trended data “bounces off” of a minimum value of one exactly at the corners where the convex envelope touches the original profile. Peaks identified by PeakCaller are marked with a green circle, whereas peaks identified by PeakFinder are marked with a red ‘X’