title: convert factor to date without producing NA's
body: <p>First I'd like to point out that other questions asked in stackoverflow couldn't bring me to the right answer. Since I'm not allowed to comment on any questions, I'm doing this entry right here. </p>
  
  <pre><code>head(mw1)
         Datum  Schluss
   1 19.07.2010 1.089,31
   2 19.07.2010 1.093,51
   3 19.07.2010 1.088,38
   4 19.07.2010 1.110,10
   5 19.07.2010 1.117,45
   6 19.07.2010 1.129,74
  </code></pre>
  
  <p>Note that <code>mw1$Datum</code> is a factor and if I want to transform it into a date by running <code>as.Date(mw1$Datum)</code>, the follwoing error occurs:</p>
  
  <pre><code>Error in charToDate(x) : 
  character string is not in a standard unambiguous format
  </code></pre>
  
  <p>According to other questions asked here, a possible solution might be:</p>
  
  <pre><code>mw1$Datum &lt;- factor("19.07.2010")
  as.Date(mw1$Datum, format = "%d/%m/%y")
  </code></pre>
  
  <p>However, it only produces NA's instead of proper dates.
  I would be delighted if someone could help me out with this problem!</p>
  
  <p>Best
  targa</p>