I am relatively new to R, so maybe I am miss something, but I now
tried the as.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 returns
>> NA for an invalid date rather than dying.
>
> So does as.Date **if you specify the format** (as you have to with your as.date:
> it has a default one):


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 be 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 also
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

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