R help - Aug 2011 - as.numeric() and POSIXct format

Hi!

I'm confused by this:
 > as.numeric(as.POSIXct(518400,origin="2001-01-01"))
[1] 978822000

I guess the problem is that as.numeric() assumes a different origin, but cannot
find
any default origin.

How can I get back the seconds from the POSIXct format? In other words, which 
the inverse function of as.POSIXct()?
I've tried as.numeric and unclass() using a origin= argument, but this does
not
work.

Thanks

Agus

-- 
Dr. Agustin Lobo
Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
LLuis Sole Sabaris s/n
08028 Barcelona
Spain
Tel. 34 934095410
Fax. 34 934110012
email: Agustin.Lobo at ija.csic.es

as.POSIXct(518400,origin='2001-01-01')
[1] "2001-01-07 PST"


as.POSIXct(as.numeric(as.POSIXct(518400,origin='2001-01-01')),origin='1970-01-01')
[1] "2001-01-07 08:00:00 PST"


On Wed, Aug 24, 2011 at 9:22 AM, Agustin Lobo
<Agustin.Lobo@ija.csic.es>wrote:
> Hi!
>
> I'm confused by this:
> > as.numeric(as.POSIXct(518400,**origin="2001-01-01"))
> [1] 978822000
>
> I guess the problem is that as.numeric() assumes a different origin, but
> cannot find
> any default origin.
>
> How can I get back the seconds from the POSIXct format? In other words,
> which the inverse function of as.POSIXct()?
> I've tried as.numeric and unclass() using a origin= argument, but this
does
> not work.
>
> Thanks
>
> Agus
>
> --
> Dr. Agustin Lobo
> Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
> LLuis Sole Sabaris s/n
> 08028 Barcelona
> Spain
> Tel. 34 934095410
> Fax. 34 934110012
> email: Agustin.Lobo@ija.csic.es
>
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