title: Get only the value of an element in an R data frame (without the index)
body: <p>I have a small data frame lie this:</p>
  
  <pre><code>&gt; testdfcompound_1
                              E1          E2
  2012-05-17 01:00:58   20.94700    2.148299
  2012-05-17 01:01:57   15.36875    2.199166
  2012-05-17 01:02:56   19.05800    2.697803
  2012-05-17 01:03:55   17.90500    2.358735
  </code></pre>
  
  <p>And I want to get only the E1 value of the 1st element, so, 20.94700.</p>
  
  <p>But I can't find a way to get it. If I try: <code>testdfcompound_1$E1[1]</code>, I'm getting:</p>
  
  <pre><code>&gt; testdfcompound_1$E1[1]
                          E1
  2012-05-17 01:00:58 20.947
  </code></pre>
  
  <p>How do I get only the 20.947 ?</p>