title: Capitalizing text of a specific column in R's data frame
body: <p>I have a data that looks like this:</p>
  
  <pre><code>GO:2000974 7,8 negative_regulation_of_pro-B_cell_differentiation Notch1 ISS
  GO:2000974 7,8 negative_regulation_of_pro-B_cell_differentiation Q9W737 IEA
  GO:0001768 4 establishment_of_T_cell_polarity Ccl19 IEA 
  GO:0001768 4 establishment_of_T_cell_polarity Ccl19 ISS 
  GO:0001768 4 establishment_of_T_cell_polarity Ccl21 IEA
  </code></pre>
  
  <p>What I want to do is to capitalize the text of the <strong>fourth</strong> column.
  So for example now we have <code>Notch1</code>, it'll then be converted to <code>NOTCH1</code>.
  What's the way to do it in R? I'm stuck with this:</p>
  
  <pre><code>dat&lt;-read.table("http://dpaste.com/1353034/plain/")
  </code></pre>