Stores the numerator, denominator, and value of a ratio as a single object.
rat(ratio, numerator, denominator, check = TRUE)Three objects belonging to the same class.
Logical. Whether to check that
    the objects are compatible.
An object equivalent to the object ratio
  except that it also belongs to the class "rat"
  and has additional attributes numerator and denominator.
The class "rat" is a simple mechanism for keeping track of
  the numerator and denominator when calculating a ratio. Its main
  purpose is simply to signal that the object is a ratio.
The function rat creates an object of class "rat"
  given the numerator, the denominator and the ratio.
  No calculation is performed; 
  the three objects are simply stored together.
The arguments ratio, numerator, denominator
  can be objects of any kind. They should belong to the same class.
  It is assumed that the relationship
  $$
    \mbox{ratio} = \frac{\mbox{numerator}}{\mbox{denominator}}
  $$
  holds in some version of arithmetic. However, no calculation is
  performed.
By default the algorithm checks
  whether the three arguments ratio, numerator,
  denominator are compatible objects, according to
  compatible.
The result is equivalent to ratio except for the
  addition of extra information.