title: R: How to add a column with a randomly chosen value from each row of a matrix?
body: <p>I'll preface this by saying I'm an R noob and that I think this may have an easy solution, but I'm struggling to find it. </p>
  
  <p>I've got a matrix with 2 columns and 1,000 rows. Keeping the rows fixed, I'd like to create a new variable that randomly chooses one of the elements from the 2 columns. For example making a simple matrix:</p>
  
  <pre><code>        matrix(c(1,1,4,6,1,3,2,1,1,7), ncol=2)
  
          [,1] [,2] [,3]
    [1,]    1    3    3
    [2,]    1    2    1  
    [3,]    4    1    4
    [4,]    6    1    1
    [5,]    1    7    7
  </code></pre>
  
  <p>In the simplified matrix above, the 3rd column (which I just added by hand) just contains a random element from either of the prior columns in the corresponding row. My question is, how would I create such a variable in R? I don't necessarily need it to be created within the matrix itself either. </p>
  
  <p>Many thanks in advance.</p>