The function as.interact extracts 
  the interpoint interaction structure from a suitable object.
  
An object of class "interact" describes an interpoint
  interaction structure, before it has been fitted to point pattern
  data. The irregular parameters of the interaction (such as the
  interaction range) are fixed, but the regular parameters
  (such as interaction strength) are undetermined.
  Objects of this class are created by the functions
  Poisson, Strauss and so on.
  The main use of such objects is in a call to ppm.
  
The function as.interact is generic, with methods for the classes
  "ppm", "fii" and "interact". 
  The result is an object of class "interact" which can be printed.