R help - Jul 2012 - c(a, b) for POSIXct objects with tzone attributes?

Hello:


       What is the recommended method for retaining the tzone attributes 
when concatonating POSIXct objects?

> (d1 <- ISOdate(1970,1,1)) # Sets the tzone attribute = GMT
[1] "1970-01-01 12:00:00 GMT"
> (d1.2 <- c(d1, d1)) # c(..) strips the tzone attribute, displays in
the time zone of the operating system
[1] "1970-01-01 04:00:00 PST" "1970-01-01 04:00:00
PST"
> attr(d1.2, 'tzone') <- 'GMT'
> d1.2 # tzone attribute manually restored
[1] "1970-01-01 12:00:00 GMT" "1970-01-01 12:00:00 GMT"


       "c" is a generic function with a method defined for objects of 
class POSIXct, so the results here were what is returned by c.POSIXct 
[as discussed with help('c.POSIXct')].


       Is there some other function like "c2", say, that tries to
retain
attributes where "c" strips all but names?


       Thanks,
       Spencer

-- 
Spencer Graves, PE, PhD
President and Chief Technology Officer
Structure Inspection and Monitoring, Inc.
751 Emerson Ct.
San Jos?, CA 95126
ph:  408-655-4567
web:  www.structuremonitoring.com

Spencer:

Just for fun, may I hazard a guess: It would be messy to retain time zones
if your were concatenating objects with more than one time zone among them.
"Normalizing"  everything to a single zone probably also makes
subsequent
operations on the results much easier.

Not that it couldn't be done -- and maybe already has been in some package.
If so, I would bet it's done via S4 classes, which would seem to be a
natural way to go.

Hopefully, you'll get a more informed and authoritative explanation,
though. ... I'm just speculating and and may be all wet.

Cheers,
Bert

On Sun, Jul 8, 2012 at 9:46 PM, Spencer Graves <
spencer.graves@structuremonitoring.com> wrote:
> Hello:
>
>
>       What is the recommended method for retaining the tzone attributes
> when concatonating POSIXct objects?
>
>
>  (d1 <- ISOdate(1970,1,1)) # Sets the tzone attribute = GMT
>>
> [1] "1970-01-01 12:00:00 GMT"
>
>> (d1.2 <- c(d1, d1)) # c(..) strips the tzone attribute, displays in
>>
> the time zone of the operating system
> [1] "1970-01-01 04:00:00 PST" "1970-01-01 04:00:00 PST"
>
>> attr(d1.2, 'tzone') <- 'GMT'
>> d1.2 # tzone attribute manually restored
>>
> [1] "1970-01-01 12:00:00 GMT" "1970-01-01 12:00:00 GMT"
>
>
>       "c" is a generic function with a method defined for objects
of class
> POSIXct, so the results here were what is returned by c.POSIXct [as
> discussed with help('c.POSIXct')].
>
>
>       Is there some other function like "c2", say, that tries to
retain
> attributes where "c" strips all but names?
>
>
>       Thanks,
>       Spencer
>
> --
> Spencer Graves, PE, PhD
> President and Chief Technology Officer
> Structure Inspection and Monitoring, Inc.
> 751 Emerson Ct.
> San José, CA 95126
> ph:  408-655-4567
> web:  www.structuremonitoring.com
>
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> and provide commented, minimal, self-contained, reproducible code.
>


-- 

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm

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