title: Reshaping dataframe in R and extracting the column name of the largest element in a row
body: <p>I have the following data frame in R</p>
  <pre><code>        n1  n2  n3  n4  n5  n6  n7  n8  n9  n10 n11 n12 n13 n14
  3557    10  5   13  3   2   8   1   9   4   7   6   12  11  14
  3558    9   10  11  1   12  7   2   14  5   8   13  4   3   6
  3559    6   7   2   14  11  10  12  5   13  8   1   9   3   4
  3560    8   11  13  1   12  3   4   2   10  9   14  7   5   6
  3561    3   9   7   8   12  5   10  2   1   6   14  11  4   13
  3562    14  2   3   10  6   12  5   13  8   9   7   4   1   11
  3563    13  6   5   9   7   8   10  11  2   3   4   1   12  14
  3564    10  11  3   5   12  7   14  4   9   8   2   13  1   6
  3565    4   8   11  7   10  3   13  14  12  2   5   9   1   6
  3566    12  9   2   11  1   14  6   10  8   3   7   5   4   13
  3567    11  12  6   7   8   14  10  13  3   4   9   2   1   5
  3568    14  7   5   11  8   12  4   3   1   9   6   13  10  2
  3569    1   11  13  2   14  6   9   7   4   12  3   5   8   10
  3570    4   5   10  8   13  7   11  3   2   14  9   12  6   1
  3571    6   9   13  14  12  2   3   7   10  8   1   5   4   11
  3572    2   6   11  5   9   13  8   10  3   4   14  7   1   12
  3573    10  13  12  9   5   14  11  6   1   3   4   8   7   2
  3574    2   10  4   7   13  5   9   8   12  11  14  3   1   6
  </code></pre>
  <p>and I want to extract the column name with which it has the largest number in that row. i.e.</p>
  <pre><code>        Choice
  3557    n14
  3558    n8
  3559    n4
  3560    n11
  3561    n11
  3562    n1
  3563    n14
  3564    n7
  3565    n8
  3566    n6
  3567    n6
  3568    n1
  3569    n5
  3570    n10
  3571    n4
  3572    n11
  3573    n6
  3574    n11
  </code></pre>
  <p>Is there any quick and efficient way to do it? Thanks in advance.</p>