create double-headed arrow paths indicating variance

Usage

ob_covariance(
  x,
  y,
  where = NULL,
  bend = 0,
  looseness = 1,
  arrow_head = arrowheadr::arrow_head_deltoid(),
  resect = 2,
  ...
)

x: object
y: object
where: exit angle
bend: Angle by which the control points are rotated
looseness: distance of control points as a ratio of the distance to the object's center (e.g., in a circle of radius 1, looseness = 1.5 means that that the control points will be 1.5 units from the start and end points.)
arrow_head: A 2-column matrix of polygon points
resect: A numeric(1) denoting millimeters or to shorten the arrow head and fins.
...: <dynamic-dots> properties passed to style