AA12     BB12
          AA1  AA2 BB1 BB2
     R1   ac   bc   bc  a
R12  R2   de   bc   cc  b
     R3   dc   ec   dc  c
R34  R4   gc   gc   gc  d

> x <- ftable(mtcars[c("cyl", "vs", "am", "gear")])
>
> ftable(x, row.vars = c(2, 4))



       cyl  4     6     8
        am   0  1  0  1  0  1
vs gear
0  3         0  0  0  0 12  0
   4         0  0  0  2  0  0
   5         0  1  0  1  0  2
1  3         1  0  2  0  0  0
   4         2  6  2  0  0  0
   5         0  1  0  0  0  0