R help - Jan 2003 - Convert numeric value to POSIXct

Hi,

How do I convert a numeric value indicating the time since 1970, back into
a POSIXct class object?  I have tried format.POSIXct and as.POSIXct
without success.

For example
> ccc
[1] "1945-01-01 15:00:00 MDT"
> ddd<- as.numeric(ccc);
> ddd
[1] -788842800
> format.POSIXct(ddd)
Error in format.POSIXct(ddd) : wrong class
> as.POSIXct(ddd)
Error in as.POSIXct.default(ddd) : Don't know how to convert `ddd' to
class "POSIXct"
>
Thanks,

Matt

Matt Pocernich
NCAR - Research Applications Program
303-497-8312

You can't safely.  Why do you want to do this?

If there is a good reason,

   structure(ddd, class=c("POSIXt", "POSIXct"))

will work currently, with no guarantees for the future.

On Wed, 22 Jan 2003, Matt Pocernich wrote:
> How do I convert a numeric value indicating the time since 1970, back into
> a POSIXct class object?  I have tried format.POSIXct and as.POSIXct
> without success.
> 
> For example
> > ccc
> [1] "1945-01-01 15:00:00 MDT"
> > ddd<- as.numeric(ccc);
> > ddd
> [1] -788842800
> > format.POSIXct(ddd)
> Error in format.POSIXct(ddd) : wrong class
> > as.POSIXct(ddd)
> Error in as.POSIXct.default(ddd) : Don't know how to convert `ddd'
to
> class "POSIXct"
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
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