R help - Jun 2009 - isolating Hour and minute form date and time

Hi everybody. I have a dataframe that contains a factor with the date
information in the format like in the example below:
"2009/05/12 11:22:31 AM"

I have been able to convert it to POSIXt using strptime

Now I want to print only the date as one vector and the time in another
vector but they must be real date and time classes so that i can use them in
calculations

to reconstruct my situation:

date=as.factor("2009/05/12 11:22:31 AM")
posix.date=strptime(date, "%Y/%m/%d %I:%M:%S %p")

I tried:

time=format(posix.date, "%A %H:%M") # For weekday, hour and minute

but the class in character. Now it prints like i want but it cannot be used
in calculations.

I would appreciate any suggestions

Thanks in advance
Christiaan

	[[alternative HTML version deleted]]

Try this and see R News 4/1 for more.
> now <- Sys.time(); now
[1] "2009-06-10 07:26:23 EDT"
> library(chron)
> ch <- as.chron(format(now))
> dd <- dates(ch); dd; dd+1
    day
06/10/09
    day
06/11/09
> tt <- times(ch) - times(dd); tt; tt+1/24
    day
07:26:23
    day
08:26:23

On Wed, Jun 10, 2009 at 7:13 AM, christiaan pauw<cjpauw at gmail.com>
wrote:
> Hi everybody. I have a dataframe that contains a factor with the date
> information in the format like in the example below:
> "2009/05/12 11:22:31 AM"
>
> I have been able to convert it to POSIXt using strptime
>
> Now I want to print only the date as one vector and the time in another
> vector but they must be real date and time classes so that i can use them
in
> calculations
>
> to reconstruct my situation:
>
> date=as.factor("2009/05/12 11:22:31 AM")
> posix.date=strptime(date, "%Y/%m/%d %I:%M:%S %p")
>
> I tried:
>
> time=format(posix.date, "%A %H:%M") # For weekday, hour and
minute
>
> but the class in character. Now it prints like i want but it cannot be used
> in calculations.
>
> I would appreciate any suggestions
>
> Thanks in advance
> Christiaan
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

There is no class for times only in R.  Your best bet is probably a 
difftime, e.g.

time <- difftime(posix.date, as.Date(posix.date), units="secs")

Allan.

christiaan pauw wrote:
> Hi everybody. I have a dataframe that contains a factor with the date
> information in the format like in the example below:
> "2009/05/12 11:22:31 AM"
>
> I have been able to convert it to POSIXt using strptime
>
> Now I want to print only the date as one vector and the time in another
> vector but they must be real date and time classes so that i can use them
in
> calculations
>
> to reconstruct my situation:
>
> date=as.factor("2009/05/12 11:22:31 AM")
> posix.date=strptime(date, "%Y/%m/%d %I:%M:%S %p")
>
> I tried:
>
> time=format(posix.date, "%A %H:%M") # For weekday, hour and
minute
>
> but the class in character. Now it prints like i want but it cannot be used
> in calculations.
>
> I would appreciate any suggestions
>
> Thanks in advance
> Christiaan
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>