Link the paired observations with a quadrilateral
link_tetragon(..., .element = NULL)<dyn-dots> A list of formulas, where each side
of the formula should be an integer or character index of the original
data, or a range_link() object defining the linked observations. Use
NULL to indicate no link on that side. You can also combine these by
wrapping them into a single list(). If only the left-hand side of the
formula exists, you can input it directly. For integer indices, wrap them
with I() to use the ordering from the layout. You can also use
waiver() to inherit values from the other group.
A element_polygon() object.
Vectorized fields will be recycled to match the total number of groups, or
you can wrap the element with I() to recycle to match the drawing
groups. The drawing groups are usually the same as the defined groups, but
they will differ when the defined group of observations is separated and
cannot be linked with a single quadrilateral. In such cases, the number of
drawing groups will be larger than the number of defined groups.