Returns a named list of numeric matrices. Each entry has dimensions
n_frames x n_sensors_in_region and contains the pressure values of
that region's sensors for each frame.
Examples
trial <- pr_example_trial("saddle_horse")
reg <- pr_mask_apply(trial)
vapply(reg, ncol, integer(1))
#> cranial_left cranial_right middle_left middle_right caudal_left
#> 36 36 48 48 40
#> caudal_right
#> 40