[Rd] POSIXlt getting sec element at 60 when converting from POSIXct

[Prof Brian Ripley]

As you say, not reproducible.  Any chance that you could put a save() file 
containing t1 somewhere we can get it?

On Tue, 14 Oct 2008, Sklyar, Oleg (London) wrote:

> In some cases rounding problems lead to creation of logically incorrect
> times in POSIXlt when converting from POSIXct.
>
> ## everything works fine for the following values:
> x = c(1223972160.00000, 1223982660.00000, 1223994660.0000)
> ## adding 0s for the epoch
> x = x + as.POSIXct("1970-01-01 00:00") -
> as.numeric(as.POSIXct("1970-01-01 00:00"))
> x
> ## [1] "2008-10-14 09:16:00 BST" "2008-10-14 12:11:00 BST"
> ## [3] "2008-10-14 15:31:00 BST"
>
> Now, numbers that look the same but originate from some calculations
> lead to the following weirdness in POSIXlt. Sorry you will not be able
> to reproduce as it is impossible to reproduce the same rounding:
>
>> as.character(as.numeric(t1))
> [1] "1223972160.00000" "1223982660.00000" "1223994660.00000"
>> class(t1)
> [1] "POSIXt"  "POSIXct"
> ## here we get a second less due to rounding errors somewhere, not too
> bad
>> t1
> [1] "2008-10-14 09:15:59 BST" "2008-10-14 12:10:59 BST"
> [3] "2008-10-14 15:30:59 BST"
>> t2 = as.POSIXlt(t1)
>> t2
> [1] "2008-10-14 09:15:59 BST" "2008-10-14 12:10:59 BST"
> [3] "2008-10-14 15:30:59 BST"
>
> ## however here we do get a real problem
>> t2$sec
> [1] 60 60 60
> ## and here as well
>> format(t2, "%Y-%m-%d %H:%M:%OS3")
> [1] "2008-10-14 09:15:60.000" "2008-10-14 12:10:60.000"
> [3] "2008-10-14 15:30:60.000"
>> format(t1, "%Y-%m-%d %H:%M:%OS3")
> [1] "2008-10-14 09:15:60.000" "2008-10-14 12:10:60.000"
> [3] "2008-10-14 15:30:60.000"
>
> Everything is back to normal with applying round (we are anyway limited
> to 15 digits):
>> t3 = round(as.numeric(t1),5) + .origin
>> t3
> [1] "2008-10-14 09:16:00 BST" "2008-10-14 12:11:00 BST"
> [3] "2008-10-14 15:31:00 BST"
>
>> sessionInfo()
> R version 2.9.0 Under development (unstable) (2008-09-30 r46585)
> x86_64-unknown-linux-gnu
>
> locale:
> C
>
> attached base packages:
> [1] splines   stats     graphics  utils     datasets  grDevices methods
>
> [8] base
>
> other attached packages:
> [1] AHLFinance_0.1.54  AHLDBConn_0.2.3    ROracle_0.5-9      DBI_0.2-4
>
> [5] RODBC_1.2-3        AHLNagLib_0.1.3    AHLCalendar_0.2.59
> AHLBase_0.1.25
>
> loaded via a namespace (and not attached):
> [1] tools_2.9.0
>
> Dr Oleg Sklyar
> Research Technologist
> AHL / Man Investments Ltd
> +44 (0)20 7144 3107
> osklyar at maninvestments.co
>
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>
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-- 
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