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<body class='hmmessage'><div dir='ltr'>Thanks for your reply Jim,<br><br>I've realized that in my data R recognizes the value "missing" as authentic NA. So, in conclusion, I really have:<br><br><font style="" face="Courier New">> DT</font><font style="" face="Courier New"><br></font><font style="" face="Courier New"><br></font><font style="" face="Courier New"> </font><font style="" face="Courier New"> id date</font><font style="" face="Courier New"><br></font><font style="" face="Courier New">1: 1 1997-04-26</font><font style="" face="Courier New"><br></font><font style="" face="Courier New">2: 1 NA</font><font style="" face="Courier New"><br></font><font style="" face="Courier New">3: 4 1998-08-25</font><font style="" face="Courier New"><br></font><font style="" face="Courier New">4: 4 NA</font><font style="" face="Courier New"><br></font><font style="" face="Courier New">5: 4 1998-11-07</font><br><br>And if I do:<br><br><font style="" face="Courier New"> > sum(is.na(DT$date))</font><br><br>The result is 2. So I've applied your suggestion and there are not changes in date variable. Can you help me?<br> </div></body>
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