title: as.numeric is rounding positive values / outputing NA for negative values
body: <p>I am trying to do something with [R] which should be extremely simple: convert values in a data.frame to numbers, as I need to test for their values and r does not recognize them as number.</p>
  
  <p>When I convert a decimal number to numeric, I get the correct value:</p>
  
  <pre><code>&gt; a &lt;- as.numeric(1.2)
  &gt; a
  [1] 1.2
  </code></pre>
  
  <p>However, when I extract a positive value from the data.frame then use as.numeric, the number is rounded up:</p>
  
  <pre><code>&gt; class(slices2drop)
  [1] "data.frame"
  &gt; slices2drop[2,1]
  [1] 1.2
  Levels: 1 1.2
  &gt; a &lt;- as.numeric(slices2drop[2,1])
  &gt; a
  [1] 2
  </code></pre>
  
  <p>Just in case:</p>
  
  <pre><code>&gt; a*100
  [1] 200
  </code></pre>
  
  <p>So this is not a problem with display, the data itself is not properly handled.</p>
  
  <p>Also, when the number is negative, I get NA:</p>
  
  <pre><code>&gt; slices2drop[2,1] &lt;- -1
  &gt; a &lt;- as.numeric(slices2drop[2,1])
  &gt; a
  [1] NA
  </code></pre>
  
  <p>Any idea as to what may be happening?</p>