On 28/12/2014 21:52, Jeff Newmiller wrote:
Very few attachment file types are allowed through the mailing list, and
yours did not make it.
I noticed that your format strings did not appear consistent... see the
format string I use below, and make sure the characters between the
numeric parts of your format are correct for your case. Did you read the
help file ?strptime ?
Note that there are two steps... importing the character data to a
POSIXct type, and then choosing how you want to display those instants
of time in whatever time zones you wish. That is, regardless of time
zone, the POSIXct value represents the same instant of time regardless
of time zone you want to display it in, while POSIXlt will in general
have different internal representations that match the external
representations.
Note that you really do need to read ?timezone, because the below code
only works if your system understands the "GMT" and "Australia/Darwin"
timezones, and that is operating-system-specific behavior. This was
successfully run on Ubuntu... you did not mention your operating system.
Correct, but for R >= 3.1.0 that help page says
' Almost all R platforms make use of a time-zone database originally
compiled by Arthur David Olson and now managed by IANA, in which
the preferred way to refer to a time zone is by a location ...'
and "GMT" is always supported although "UTC" is preferred.
All the platforms documented in 'R Installation and Administration' do
make such use; however occasionally we hear of new ports, hence the
cautious use of 'Almost'.
However, we were also not told the R version ....
tst <- "2014-12-25 00:00" # GMT
tstct <- as.POSIXct( tst, format="%Y-%m-%d %H:%M", tz="GMT" )
tstct
[1] "2014-12-25 GMT"
unclass(tstct)
[1] 1419465600
attr(,"tzone")
[1] "GMT"
tstlt <- as.POSIXlt( tstct, tz="Australia/Darwin" )
tstlt
[1] "2014-12-25 09:30:00 ACST"
unclass(tstlt)
$sec
[1] 0
$min
[1] 30
$hour
[1] 9
$mday
[1] 25
$mon
[1] 11
$year
[1] 114
$wday
[1] 4
$yday
[1] 358
$isdst
[1] 0
$zone
[1] "ACST"
$gmtoff
[1] 34200
attr(,"tzone")
[1] "Australia/Darwin" "ACST" "ACDT"
tstct2 <- as.POSIXct( tstlt )
tstct2
[1] "2014-12-25 09:30:00 ACST"
unclass(tstct2)
[1] 1419465600
attr(,"tzone")
[1] "Australia/Darwin"
On Sun, 28 Dec 2014, Faranak Golestaneh wrote:
Dear Friends, I?ve just started using R. I am working on a database
containing date-time as well as numeric values. Firstly I have changed
the
class of the data/time column from factor to POSIXlt. Time and date are
based on UTC time but I need to change them to a local time ( not my
local
time, my zone is Singapore but the data are from Australia) so I need to
change the time and date to Australia time say e.g AEST. I tried one
way or
another but all failed. The following is example of the command I used.
Also one of my .CSV files is attached.
Data_Power <- read.table("train15.csv",header = TRUE, sep = ",",
row.names
= NULL);
Date_clm=Data_Power$TIMESTAMP;
Date_original <- strptime(Date_clm, "%Y %m %d %H:%M", tz="GMT")
Date_local =format(Date_original, format="%c", tz="America/New_York")
Date_local <- strptime(Date_original, "%Y %m %d %H:%M +0800")
Date_local=as.POSIXlt(Date_original, "Australia/Darwin")
Date_local=as.POSIXlt(Date_original, " AEST ")
I would be so thankful if you help me out. Thanks
Cheers,
Faranak
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Emeritus Professor of Applied Statistics, University of Oxford
1 South Parks Road, Oxford OX1 3TG, UK
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