R help - Feb 2008 - How do I use as.Date when day values are missing?

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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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
>
>
>
>
>
>
>
>     
____________________________________________________________________________________
> Never miss a thing.  Make Yahoo your home page.
>
>        [[alternative HTML version deleted]]
>
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