[R] Number of Days Between Dates: Incorrect Results For DateCalucations.

[Dimitris Rizopoulos]

check again your results with as.integer() replaced by round(); check 
also ?as.integer for its usage.

I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://www.med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: <gerald.herbert at hubbardbreeders.com>
To: <r-help at stat.math.ethz.ch>
Sent: Tuesday, February 21, 2006 4:48 PM
Subject: [R] Number of Days Between Dates: Incorrect Results For 
DateCalucations.


> In some cases, incorrect results are produced by the code below 
> intended to
> calculate the number of days between 2 dates.  The year in question 
> was a
> leap year.
>
> Note the results for 2004-04-04 and 2004-04-05 are the same! They 
> should be
> 37 and 38 respectively.
>
>> as.integer(as.POSIXct("2004-04-02") - as.POSIXct("2004-02-27"))
> [1] 35
>> as.integer(as.POSIXct("2004-04-03") - as.POSIXct("2004-02-27"))
> [1] 36
>> as.integer(as.POSIXct("2004-04-04") - as.POSIXct("2004-02-27"))
> [1] 37
>> as.integer(as.POSIXct("2004-04-05") - as.POSIXct("2004-02-27"))
> [1] 37
>> as.integer(as.POSIXct("2004-04-06") - as.POSIXct("2004-02-27"))
> [1] 38
>
>
>
>> as.integer(difftime(as.POSIXct("2004-04-06"),
> as.POSIXct("2004-02-27"),units="days"))
> [1] 38
>> as.integer(difftime(as.POSIXct("2004-04-04"),
> as.POSIXct("2004-02-27"),units="days"))
> [1] 37
>> as.integer(difftime(as.POSIXct("2004-04-05"),
> as.POSIXct("2004-02-27"),units="days"))
> [1] 37
>
> It appears that difftime() and "-" are producing invalid results.
>
>
> Regards,
>
> Gerald Herbert
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
> 


Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm