[R] POSIXct value display incorrect for some values

[jim holtman]

This is basically FAQ 7.31.  WIth floating point number, you have
about 15 digits of significance, so if you look at the value:

>> as.numeric(as.POSIXct('2010-06-03 9:03:58.324'))
> [1] 1275581038.3239998817

when you get down to the milliseconds, this is about as much accuracy
as you will get based on using POSIXct with dates around this
century..  If you need more accuracy, then maybe you only use the
hours and may have to have separate values for the date and the time
based on the accuracy of floating point.

On Thu, Jan 19, 2012 at 3:57 PM, Curt Seeliger
<Seeliger.Curt at epamail.epa.gov> wrote:
> First, the reproducable example, showing how converting from character to
> POSIXct to character changes the milliseconds in the first time stamp
> though not in the second:
>
>> as.POSIXct('2010-06-03 9:03:58.324')
> [1] "2010-06-03 09:03:58.323 PDT"
>
>> as.POSIXct('2010-06-03 9:03:58.325')
> [1] "2010-06-03 09:03:58.325 PDT"
>
> This seems to be due to truncation of the numeric value of the POSIX
> object during conversion to character:
>
>> as.numeric(as.POSIXct('2010-06-03 9:03:58.324'))
> [1] 1275581038.3239998817
>
> Neither format() nor round() seem to be of assistance here.  Anyone got a
> solution?
>
>> as.POSIXct(round(as.double(as.POSIXct('2010-06-03 09:03:58.324')),
> digits=3), origin=(as.POSIXct('1970-01-01')))
> [1] "2010-06-03 17:03:58.323 PDT"
>> format(as.POSIXct('2010-06-03 09:03:58.324'), "%Y-%m-%d %H:%M:%OS4")
> [1] "2010-06-03 09:03:58.3239"
>
> Thanks,
> cur
> --
> Curt Seeliger, Data Ranger
> Raytheon Information Services - Contractor to ORD
> seeliger.curt at epa.gov
> 541/754-4638
>
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>
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-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.