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Co-occurrence
A co-occurrence is 2 annotations of different types that overlap in time, or that fall within a short window of each other. In both cases the 2 things happen together. You can then ask if the pair happens often, or only once or twice.
Example: A teacher points at the board while she asks a question. The Gesture annotation and the Question annotation cover the same seconds. That pair is one co-occurrence. If you find 40 such pairs, gesture and question go together in this lesson.
Why it matters in GRAPE MARS
The Co-occurrence Heatmap module counts each pair of annotation types that meet in this way. It uses a window of 2 seconds by default, so 2 marks that nearly touch still count as a pair. You can change the window with the Co-occurrence window slider. The heatmap shows which pairs are common and which are rare.