title: Removing duplicate rows from a CSV file
body: <p>I want to remove CSV rows that have the same value in two columns. <code>uniq</code> can be passed as a block, but I cannot figure it out:</p>
  
  <pre><code>CSV.open( "csv/competition-duped.csv", 'w' ) do | csv |
    CSV.read( file ).uniq{ | column | column.values_at( column[ 3 ], column[ 7 ] ) }.each do | row |
      csv &lt;&lt; row
    end
  end
  </code></pre>
  
  <p>Further to this, I may have found the solution.</p>
  
  <pre><code>CSV.read( file ).uniq{ | column | [ column[ 3 ], column[ 7 ] ] }.each do | row |
  </code></pre>