title: Unexpected value for length of a vector in R
body: <p>I have the character vector below</p>
  
  <pre><code>a = c("2009-07-31 18:00:33", "2009-07-31 18:00:38", "2009-07-31 18:00:43",  "2009-07-31 18:00:49", "2009-08-01 01:58:49", "2009-08-01 01:53:16",  "2009-08-01 08:04:13", "2009-08-01 16:16:13")
  </code></pre>
  
  <p>I want to convert this to time objects so I do this:</p>
  
  <pre><code>b = strptime(a, "%Y-%m-%d %H:%M:%S")
  </code></pre>
  
  <p>Why do a and b have different lengths?</p>
  
  <pre><code>&gt; length(a)
  [1] 8
  &gt; length(b)
  [1] 9
  </code></pre>