[R] Time conversion

Richard.Cotton at hsl.gov.uk
Thu, 02 Oct 2008 14:16:57 -0000

> I'm trying to convert a variable that is imported from CSV into a
datetime,I'm
> trying to use the strptime function but with no joy, can anyone offer
any
> advise?
>
> i have a vector
> timestamp
> 07-07-2008-21:03:55
> 07-07-2008-19:52:55
> 07-07-2008-19:54:14
> 07-07-2008-15:24:01
> 07-07-2008-13:39:17
> 07-07-2008-13:39:55
>
>
> timestamp<-strptime(timestamp,"%d-%m-%y-%H:%M:%S")
> ## then filter on the datetime
> time<-ifelse(timestamp> "07-08-2008-00:00:00", TRUE, FALSE)

1. Since the years are of the form YYYY, your format vector should be
"%d-%m-%Y-%H:%M:%S".

2. You don't need the ifelse call if you the last two arguments are just
TRUE, FALSE

3. You do need to call strptime on your comparision date.

timestamp <- c("07-07-2008-21:03:55",
   "07-07-2008-19:52:55",
   "07-07-2008-19:54:14",
   "07-07-2008-15:24:01",
   "07-07-2008-13:39:17",
   "07-07-2008-13:39:55")
timestamp <- strptime(timestamp,"%d-%m-%Y-%H:%M:%S")
time <- timestamp >
strptime("07-08-2008-00:00:00","%d-%m-%Y-%H:%M:%S")

Regards,
Richie.

Mathematical Sciences Unit
HSL


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