[R] pointers needed to expected values of fractions

[ivo welch]

I apologize in advance for a more statistical question.  I am trying
to find out whether a transformation of two random variables X and Y (
z= g(X,Y) ) exists whose expected value is E(X)/E(Y).  obviously, it
ain't E(X/Y).  is there a book or place where I could learn this?
(Also, I would be interested to learn more about the properties of
E(X/Y) if they have been worked out (and not just when X and Y are
independent), so if there is a book for this one, I would again be
quite interested, too.)  this is not an R topic, so please email me
directly if you know where I could look.  thanks in advance.  again,
apologies for the clutter... /iaw