title: Can't get last column of data.frame
body: <p>Consider the following data:</p>
  
  <pre><code>subjectName &lt;- c("John Doe", "Jane Doe")
  temperature &lt;- c(98.1, 98.6)
  gender &lt;- factor(c('male', 'female'), levels = c('male','female'))
  
  ptData &lt;- data.frame(subjectName, temperature, gender, stringsAsFactors = F)
  </code></pre>
  
  <p>When I call:</p>
  
  <pre><code>ptData[,1]
  </code></pre>
  
  <p>I receive the first column, as expected.  However, when I call:</p>
  
  <pre><code>ptData[,-1]
  </code></pre>
  
  <p>R fails to give me the last column.  Instead, it outputs the last two:</p>
  
  <pre><code>  temperature gender
  1        98.1   male
  2        98.6 female
  </code></pre>
  
  <p>Why doesn't my call work as expected?</p>