[R] How do I use as.Date when day values are missing?

[Peter Dalgaard]

Gabor Grothendieck wrote:
> In looking at this again here is a slight simplification.  Its now
> only one line:
>
>   
>> library(chron)
>> x <- c("01/00/05", "01/22/06")
>> as.chron(sub("/00/", "/15/", x)) + (regexpr("/00/", x) > 0) / 2
>>     
> [1] (01/15/05 12:00:00) (01/22/06 00:00:00)
>   
You don't really need chron here, do you?

as.Date(sub("/00/", "/15/", x), format="%m/%d/%y")

(The format spec seems to have been left out below. Also, beware the
system-dependence of %y.)
>
> On Sun, Feb 24, 2008 at 9:45 PM, Gabor Grothendieck
> <ggrothendieck at gmail.com> wrote:
>   
>> It really depends on what you want to do with them but one possibility
>> might be to represent them as chron dates and use a time of 0 for true dates
>> and noon for missing dates replacing the missing day with 01 or 15 or some
>> other day:
>>
>>     
>>> library(chron)
>>> x <- c("01/00/05", "01/22/06")
>>> no.day <- regexpr("/00/", x) > 0
>>> as.chron(ifelse(no.day, sub("/00/", "/15/", x), x )) + no.day/2
>>>       
>> [1] (01/15/05 12:00:00) (01/22/06 00:00:00)
>>
>> We can then tell which have the incomplete dates with as.numeric(xx) %% 1 > 0
>>
>>
>>
>> On Sun, Feb 24, 2008 at 9:00 PM, Anupa Fabian <anupa.fabian at yahoo.com> wrote:
>>     
>>> I have a data frame which contains some valuable date information. But for a few of the dates, the day information missing .
>>>
>>> Viz:
>>>       
>>>> interesting.data$date
>>>>         
>>> [1] "1/22/93" "1/22/93" "1/23/93" "1/00/93" "1/28/93" "1/31/93" "1/12/93"
>>>
>>> i.e. for dates where the day info is missing, the "%d" part of the "%m/%d/%yy" format is simply represented as "00".
>>>
>>> When I apply as.Date to the date information, the dates which don't contain exact day information are converted to "NA".
>>>
>>> Viz:
>>>       
>>>> as.Date(interesting.data$date)
>>>>         
>>> [1] "1993-01-22" "1993-01-22" "1993-01-23" NA "1993-01-28" "1993-01-31" "1993-01-12"
>>>
>>> Is there a way of using the as.Date function when I only have partial dates (eg missing day information  which is represented as "00", as above) such
>>>  that the date isn't represented as NA?
>>>
>>> Thanks,
>>> Anupa
>>>
>>>
>>>
>>>
>>>
>>>
>>>
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>>>       
>
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>   


-- 
   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
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