[R] Data frame which includes a non-existent date

[Richard M. Heiberger]

Frank,

Dates are extremely difficult.  I recommend you do not attempt to do
your own data computations with paste().
Use the lubridate package.
> install.packages(lubridate)
> library(lubridate)
Read the end section of
> vignette("lubridate")

>From that you will most likely be wanting one of these
>  ymd("19480229") %m+% years(65)
[1] "2013-02-28 UTC"

> daydiff <-  ymd("19480229") - floor_date(ymd("19480229"), "month")
> floor_date(ymd("19480229"), "month") + years(65) + daydiff
[1] "2013-03-01 UTC"
>

Rich

On Thu, Sep 18, 2014 at 11:22 AM, Frank S. <f_j_rod at hotmail.com> wrote:
>
>
> Hi to all members of the list,
>
> I have a data frame with subjects who can get into a certain study from 2010-01-01 onwards. Small example:
>
> DF <- data.frame(id=as.factor(1:3), born=as.Date(c("1939/10/28", "1946/02/23", "1948/02/29")))
>
>   id       born
> 1  1 1939-10-28
> 2  2 1946-02-23
> 3  3 1948-02-29
>
> Now, I add a new column "enter" as follows:
>
> 1) If the subject is 65 years old before 2010-01-01, then enter=2010-01-01.
> 2) If the subject i NOT 65 years old before 2010-01-01, then enter="Date on which subject reach 65"
>
> DF_new <- data.frame(DF,
>  enter= as.Date( ifelse(unclass(round(difftime(open, DF$born)/365.25,1))<=65,
> paste(year(DF$born)+65,substr(DF$born,6,10),sep="-"), paste(open))) )
>
> The problem is that the DF_new output has a NA in subject id=3:
>
>   id       born      enter
> 1  1 1939-10-28 2010-01-01
> 2  2 1946-02-23 2011-02-23
> 3  3 1948-02-29       <NA>
>
> I'm afraid (I'm not really sure) that the matter is that subject id=3 would reach 65 yr at 2013-02-29, but this date does not exist,
> so R gives a missing.
>
> Can any help me?
>
> Thank you!!!
>
>
>
>
>
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>
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