Derived from the index rather than declared, in the unit the index is in – so a frame indexed by frame number has an interval in frames, and one indexed by seconds has it in seconds.
Details
Measured per key: identity plus temporal context. The index restarts in each group, so pooling them would measure the restarts rather than the sampling.
Measured again whenever the rows or the index change: by
dplyr::filter(), dplyr::slice(), [, a dplyr::mutate() of the
index or a key, and the other dplyr verbs anicore provides methods for.
A frame that keeps every third row of a 30 Hz recording then reports the
10 Hz spacing it now has, and validate_anipoint() says that its
sampling_rate no longer matches.
Examples
af <- example_anipoint(n_obs = 5, n_individuals = 2, n_keypoints = 1)
get_sampling_interval(af)
#> [1] 1