This is known, and not easy to solve given the way dispatch works for
binary operators.
The documentation was broken when Ops.difftime was introduced. You have
found the known fix ....
On Wed, 21 Feb 2007, Jeffrey Horner wrote:
> Jeffrey Horner wrote:
>> Hello,
>>
>> ?DateTimeClasses states that "one can add or subtract a number of
>> seconds or a 'difftime' object from a date-time object, but not add two
>> date-time objects."
>>
>> So, is the below expected behavior?
>>
>> > x <- Sys.time()
>> > x
>> [1] "2007-02-21 16:19:56 CST"
>> > x + as.difftime("1","%H")
>> [1] "2007-02-21 16:19:57 CST"
>> Warning message:
>> Incompatible methods ("+.POSIXt", "Ops.difftime") for "+"
>>
>> "+.POSIXt" does behave as expected, though:
>>
>> > "+.POSIXt"(x,as.difftime("1","%H"))
>> [1] "2007-02-21 17:19:56 CST"
>>
>> > R.version
>> _
>> platform i686-pc-linux-gnu
>> arch i686
>> os linux-gnu
>> system i686, linux-gnu
>> status Under development (unstable)
>> major 2
>> minor 5.0
>> year 2007
>> month 01
>> day 07
>> svn rev 40398
>> language R
>> version.string R version 2.5.0 Under development (unstable) (2007-01-07
>> r40398)
>
> Oops! I thought I ran this on the latest revision, but the same behavior
> is exhibited in r40774:
>
> > x <- Sys.time()
> > x
> [1] "2007-02-21 16:44:16 CST"
> > x + as.difftime("1","%H")
> [1] "2007-02-21 16:44:17 CST"
> Warning message:
> Incompatible methods ("+.POSIXt", "Ops.difftime") for "+"
> > R.version
> _
> platform i686-pc-linux-gnu
> arch i686
> os linux-gnu
> system i686, linux-gnu
> status Under development (unstable)
> major 2
> minor 5.0
> year 2007
> month 02
> day 21
> svn rev 40774
> language R
> version.string R version 2.5.0 Under development (unstable) (2007-02-21
> r40774)
>
>
> Jeff
>
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
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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