The directional arrows point towards the nearest goal line from the yardage marker they are closest to. These arrows are described by their base (which runs parallel to the goal line) and their length, which extends from the tip to the base
football_directional_arrow(arrow_base = 0, arrow_length = 0)
A data frame of the bounding coordinates of the directional arrow
The length of the base of the arrow
The length of the arrow from tip to base