[R] simple question on picking out some rows of a matrix/data frame

[Roger Levy]

Hi,

I have a simple question about matrix/data frame manipulation.  I have
a data frame that looks a something like this

  X    Y    Z
  1    0    "apples"
  -1   -1   "oranges"
  ...
  0    -1   "bananas"

and I'd like to pull out all the rows for which X and Y are (un)equal
into a submatrix.

How can I do that?

Many thanks,

Roger Levy