title: matrix %in% matrix
body: <p>Suppose I have two matrices, each with two columns and differing numbers of row. I want to check and see which pairs of one matrix are in the other matrix. If these were one-dimensional, I would normally just do <code>a %in% x</code> to get my results. <code>match</code> seems only to work on vectors.</p>
  
  <pre><code>&gt; a
        [,1] [,2]
  [1,]    1    2
  [2,]    4    9
  [3,]    1    6
  [4,]    7    7
  &gt; x
       [,1] [,2]
  [1,]    1    6
  [2,]    2    7
  [3,]    3    8
  [4,]    4    9
  [5,]    5   10
  </code></pre>
  
  <p>I would like the result to be <code>c(FALSE,TRUE,TRUE,FALSE)</code>.</p>