[R] help with calculating the differences between dates

[Uwe Ligges]

Tom Cohen wrote:
> Dear list, 
>   How can I calculate the difference in days between the eventdate and basedate in the below dataset? 
>   
>      id basedate   outcome.3 eventdate     daydiff
> 1  1001 1999-09-28         2 1999-10-01    3
> 2  1002 1999-09-22         1           
> 3  1003 2000-01-19         1           
> 4  1004 2004-01-25         2 2004-02-03    9
> 5  1005 2005-08-11         1           
> 6  1006 2000-07-04         1 2001-05-29    
> 7  1007 2004-02-12         1 2004-11-18
> 8  1008 2006-01-18         2 2006-02-02
> 9  1009 2005-04-29         2 2005-06-14
> 10 1010 2006-03-17         2 2006-03-31
> 11 1011 2000-03-21         2 2000-03-28
> 12 1012 2004-07-12         1 2006-11-28
> 13 1013 2000-02-24         1           
> 14 1014 2003-04-17         1           
> 15 1015 2000-04-05         1         


Given they are in some appropriate time format (e.g. when reading 
specify colClasses = "POSIXct" for those columns or use strptime() on 
the colummns later on):

difftime(x$eventdate, x$basedate, "days")

Uwe Ligges




> Thanks for any help,
> Tom
> 
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