Tests whether two or more objects of the same class are compatible.
compatible(A, B, …)Two or more objects of the same class
Logical value: TRUE if the objects are compatible, and FALSE
  if they are not.
This generic function is used to check whether the
  objects A and B (and any additional
  objects …) are compatible.
What is meant by ‘compatible’ depends on the class of object.
There are methods for the classes "fv", "fasp",
  "im" and "unitname". See the documentation for these
  methods for further information.
compatible.fv,
  compatible.fasp,
  compatible.im,
  compatible.unitname