If r is a number, square(r)
  is a shortcut for creating a window object
  representing the square 
  \([0,r] \times [0,r]\).
  It is equivalent to the command
  owin(c(0,r),c(0,r)).
If r is a vector of length 2, then
  square(r) creates the square with x and y coordinates
  ranging from r[1] to r[2].
  
unit.square creates the unit square
  \([0,1] \times [0,1]\).
  It is equivalent to
  square(1) or square() or owin(c(0,1),c(0,1)).
These commands are included for convenience,
  and to improve the readability of some code.