X-axis shows ID of frames included in the reference library of HD 206893 using the PCC metric. The Y-axis shows the number of times a given reference frame is among the top R=25 most similar frames when considering all the 576 scientific frames of HD 206893. A threshold N=50 (red line) was used to build the reference library; we therefore only show the reference frames present more than 50 times in the top 25 most similar frames here. This criteria (R=25, N=50) is relatively restrictive in this example, as we end up with only 36 frames in the reference library.