R help - Jun 2006 - Suspicious behaviour of sort on POSIXct vectors in R-2.3.0 and R-2.3.1

Hi ,

When I sort a vector of POSIXct values in R-2.3.0 and R-2.3.1, I get a
vector of numeric values and this gets some of my code to crash (class
object creation). Is that a R bug?

In the mean time. I'll try to override the sort function for the POSIXct
objects.

Thanks,

Patrick Gu?vel
Head of quantitative research for electronic trading


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intende...{{dropped}}

Use order instead:

x <- as.POSIXct(Sys.Date() + 10:1)
x[order(x)]


On 6/6/06, patrick.guevel at uk.bnpparibas.com
<patrick.guevel at uk.bnpparibas.com> wrote:
> Hi ,
>
> When I sort a vector of POSIXct values in R-2.3.0 and R-2.3.1, I get a
> vector of numeric values and this gets some of my code to crash (class
> object creation). Is that a R bug?
>
> In the mean time. I'll try to override the sort function for the
POSIXct
> objects.
>
> Thanks,
>
> Patrick Gu?vel
> Head of quantitative research for electronic trading
>
>
> This message and any attachments (the "message") is\
intende...{{dropped}}
>
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http://www.R-project.org/posting-guide.html
>

On Tue, 6 Jun 2006, patrick.guevel at uk.bnpparibas.com wrote:
> Hi ,
>
> When I sort a vector of POSIXct values in R-2.3.0 and R-2.3.1, I get a
> vector of numeric values and this gets some of my code to crash (class
> object creation). Is that a R bug?
No, it is as documented: see ?sort

      As from R 2.3.0, all attributes are removed from the return value
      except names, which are sorted.  (If 'partial' is specified even
      the names are removed.)

Note, the class is an attribute.  For many classes sorting destroys the 
appropriateness of the class.
> In the mean time. I'll try to override the sort function for the
POSIXct
> objects.
You can restore the class if appropriate.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
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

{Diverted to R-devel}
>>>>> "BDR" == Prof Brian Ripley <ripley at
stats.ox.ac.uk>
>>>>>     on Tue, 6 Jun 2006 21:14:01 +0100 (BST) writes:
    BDR> On Tue, 6 Jun 2006, patrick.guevel at uk.bnpparibas.com
    BDR> wrote:
    >> Hi ,
    >> 
    >> When I sort a vector of POSIXct values in R-2.3.0 and
    >> R-2.3.1, I get a vector of numeric values and this gets
    >> some of my code to crash (class object creation). Is that
    >> a R bug?

    BDR> No, it is as documented: see ?sort

    BDR>       As from R 2.3.0, all attributes are removed from
    BDR> the return value except names, which are sorted.  (If
    BDR> 'partial' is specified even the names are removed.)

    BDR> Note, the class is an attribute.  For many classes
    BDR> sorting destroys the appropriateness of the class.

Indeed, and I agree this a good change.
However, the above also suggests that ideally,  sort() would be
a generic function.

One good reason for  sort()  not being generic now is the fact
that method dispatch costs a bit, *and* that we like sort() to
be really fast.
One way to achieve a generic sort() and keep the possibility of
of very fast sort() --- similarly to  rep() and rep.int()
would be to rename the current sort into something like
sortNum() {"Num" for numeric}, make sort() into a generic,
and replace sort() by sortNum() in those code parts which need
to remain optimally fast.


    >> In the mean time. I'll try to override the sort function
    >> for the POSIXct objects.

    BDR> You can restore the class if appropriate.