title: Date time conversion and extract only time
body: <p>Want to change the class for Time to POSIXlt and extract only the hours minutes and seconds</p>
  
  <pre><code>str(df3$Time)
  chr [1:2075259] "17:24:00" "17:25:00" "17:26:00" "17:27:00" ...
  </code></pre>
  
  <p>Used the strptime function</p>
  
  <pre><code>df33$Time &lt;- strptime(df3$Time, format = "%H:%M:%S") 
  </code></pre>
  
  <p>This gives the date/time appended</p>
  
  <pre><code>&gt; str(df3$Time)
   POSIXlt[1:2075259], format: "2015-08-07 17:24:00" "2015-08-07 17:25:00" "2015-08-07 17:26:00" ...
  </code></pre>
  
  <p>Wanted to extract just the time without changing the POSIXlt class. using the strftime function </p>
  
  <pre><code>df3$Time &lt;- strftime(df3$Time, format = "%H:%M:%S") 
  </code></pre>
  
  <p>but this converts the class back to "char" - </p>
  
  <pre><code>&gt; class(df3$Time)
  [1] "character"
  </code></pre>
  
  <p>How can I just extract the time with class set to POSIX or numeric...</p>