title: Count rows in multiple csv's, write to csv's as new column in descending order
body: <p>I need help editing multiple csv's within a folder.  I need to count the number of rows in each file, and add a new column to the files.  The new column should have the number of rows as the first row in the column, and then descend by 1 for each subsequent row.</p>
  
  <pre><code>Current:
  ID  V1  V2  V3
  1   0.4625  0.917
  2   0.9324  0.248
  3   0.6691  0.781
  4   0.1935  0.330
  
  Proposed:
  ID  V1   V2  V3   newcol  
  1   0.4  25  0.9  5
  2   0.9  24  0.2  4
  3   0.6  91  0.7  3
  4   0.1   5  0.3  2
  5   0.2  44  0.5  1
  </code></pre>
  
  <p>Anyone have any ideas? I've been playing around with the terminal and trying to do it that way.  I also have some minor experience with r.  I'm also using a mac if that helps.</p>
  
  <p>Thanks!</p>