Dear Brian,

I dont understand what you mean.  The thread was about the as.Date which you
suggested to be used instead of the as.date.  Following your advice I tried
the as.Date and have questions about the observed behaviour, which was
surprising to me.  Is this what you call hijacking?  Do you mean I ought
start a new thread instead?  I thought my question were relevant to the
threads' subject.  I am sorry if it were not.

So here is the questions once again:  why do the as.Date behave as in my
examples below, is this intended?



On Thu, Jan 22, 2009 at 3:55 PM, Brian D Ripley <ripley@stats.ox.ac.uk>wrote:

> You've hijacked a thread here.
>
>
> On Thu, 22 Jan 2009, Marie Sivertsen wrote:
>
>
>> I am relatively new to R, so maybe I am miss something, but I now tried
>> the a
>> s.Date now and have problems understanding how it works (or don't work as
>> it seem).
>>
>> Brian D Ripley wrote:
>> > On Thu, 22 Jan 2009, Terry Therneau wrote:
>> >>
>> >> One idea is to use the as.date function, for the older (and less
>> capable) 'date'
>> >> class.  This is currently loaded by default with library(survival).  It
>> re
>> turns
>>
>> >> NA for an invalid date rather than dying.
>> >
>> > So does as.Date *if you specify the format* (as you have to with your
>> as.da
>> te:
>> > it has a default one):
>
>

My examples:



>
>> as.Date("2001/1/1")
>> Works fine
>> as.Date("1/1/2001")
>> Prints "1-01-20" ???
>> as.Date("13/1/2001")
>> Prints "13-01-20" ???
>>
>> as.Date("1/13/2001")
>> Prints error: not in standard unambigous format
>> It seems that as if both "1/1/2001" and "13/1/2001" were considered by R
>> to b
>> e in a standard unambiguous format (or otherwise an error be reported?)
>> and yet they
>>
>>
>> are parsed incorrectly according to what one could think is obvious.  It
>> is a
>> lso surprizing that not only "13/1/2001" but also "1/2/2001" and
>> "2/1/2001" are successful but incorrect parsed as if they are unambiguous,
>> and yet
>> "13/1/2001" is ambiguous, though there is really just one way to parse it
>> meaningfully.
>> I think the strings that are incorrectly parsed should raise errors, and
>> the last example should be succesful parsed.  What is the reason for the
>> observed
>> ?
>>
>>
>>


Mvh.
Marie



>
>>
> --
> Brian D. Ripley,                  ripley@stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/<http://www.stats.ox.ac.uk/%7Eripley/>
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>

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