[R] comparing two data.frames

[Adrian Johnson]

Dear group,
I have two data.frames X and Y identical except for values.

> X
    gene   fc
 A1CF   -0.10050677
A2BP1  -2.03093217
A2M      -0.09092704
A4GALT 0.04124563
A4GNT  -0.10336042

> Y
       gene   fc
A1CF      -0.085709770
A2BP1      1.058642812
A2M         0.142530426
A4GALT    0.009463123
A4GNT     -0.057584059

I am interested in finding A2BP1 that is negative in X and positive in
Y. How could I search for reverse values.
thank you.
-Ad