title: R coerce data frame to numeric
body: <p>RandomForest has returned object, prd, which is class numeric with indices:</p>
  
  <pre><code>&gt; prd
        298       252       373       117         0        16       442        74 
  4397.9232 1826.1264 1787.1963 1388.8097 1075.7217  873.9856 1602.7068 1775.1237 
  class(prd)
  [1] "numeric"
  </code></pre>
  
  <p>I want to do a correlation test, which means getting obs in the same format. Currently, obs is a one-column data frame:</p>
  
  <pre><code>&gt; obs
         e2004MeanY
  298       4261
  252       1821
  373       1710
  117       1138
  </code></pre>
  
  <p>How do I convert obs to the correct format? I can't figure out how to tie the indices to the values in a numeric. </p>