Sets the sampling rate (in Hz) on an aniframe() or anievent() and,
if the object's unit_time is currently "frame" or "unknown",
converts the temporal columns from frames to seconds using
1 / sampling_rate. If unit_time is already an SI unit, only the
metadata is updated.
Usage
set_sampling_rate(data, sampling_rate)
# S3 method for class 'aniframe'
set_sampling_rate(data, sampling_rate)
# S3 method for class 'anievent'
set_sampling_rate(data, sampling_rate)