I have a following time stamps.
outlist
"19980202_0810" "19980202_0815" "19980202_0820"
I want to have
"1998-02-02T08:10:00Z" "1998-02-02T08:15:00Z" "1998-02-02T08:20:00Z"
All I can do either "1998-02-02 08:10:00 PST".
time_obj = strptime(outlist, format = "%Y%m%d_%H%M")
strptime is the import function; strftime is the format (output) function although I think most people would just use format:
outlist <- c("19980202_0810", "19980202_0815", "19980202_0820")
time_obj=strptime(outlist, format = "%Y%m%d_%H%M")
format( time_obj , format="%Y-%m-%dT%H:%M:%SZ")
#[1] "1998-02-02T08:10:00Z" "1998-02-02T08:15:00Z" "1998-02-02T08:20:00Z"
At the moment these are POSIXlt items:
> class(time_obj)
[1] "POSIXlt" "POSIXt"
It would be safer to convert to POSIXct:
> time_obj=as.POSIXct(outlist, format = "%Y%m%d_%H%M")
> time_obj
[1] "1998-02-02 08:10:00 PST" "1998-02-02 08:15:00 PST" "1998-02-02 08:20:00 PST"
> class(time_obj)
[1] "POSIXct" "POSIXt"
POSIXlt objects are not handled well in data.frames.
Edit: The print method for POSIXct objects is documented in ?DateTimeClasses and the help page for format.POSIXct is at``srtftime` which I already cited:
strftime(time_obj, tz = "UTC")
[1] "1998-02-02 16:10:00" "1998-02-02 16:15:00" "1998-02-02 16:20:00"
Related
This question already has answers here:
Convert date-time string to class Date
(4 answers)
Closed 3 years ago.
I have date&time stamp as a character variable
"2018-12-13 11:00:01 EST" "2018-10-23 22:00:01 EDT" "2018-11-03 14:15:00 EDT" "2018-10-04 19:30:00 EDT" "2018-11-10 17:15:31 EST" "2018-10-05 13:30:00 EDT"
How can I strip the time from this character vector?
PS: Can someone please help. I have tried using strptime but I am getting NA values as a result
It's a bit unclear whether you want the date or time but if you want the date then as.Date ignores any junk after the date so:
x <- c("2018-12-13 11:00:01 EST", "2018-10-23 22:00:01 EDT")
as.Date(x)
## [1] "2018-12-13" "2018-10-23"
would be sufficient to get a Date vector from the input vector x. No packages are used.
If you want the time then:
read.table(text = x, as.is = TRUE)[[2]]
## [1] "11:00:01" "22:00:01"
If you want a data frame with each part in a separate column then:
read.table(text = x, as.is = TRUE, col.names = c("date", "time", "tz"))
## date time tz
## 1 2018-12-13 11:00:01 EST
## 2 2018-10-23 22:00:01 EDT
I think the OP wants to extract the time from date-time variable (going by the title of the question).
x <- "2018-12-13 11:00:01 EST"
as.character(strptime(x, "%Y-%m-%d %H:%M:%S"), "%H:%M:%S")
[1] "11:00:01"
Another option:
library(lubridate)
format(ymd_hms(x, tz = "EST"), "%H:%M:%S")
[1] "11:00:01"
The package lubridate makes everything like this easy:
library(lubridate)
x <- "2018-12-13 11:00:01 EST"
as_date(ymd_hms(x))
You can use the as.Date function and specify the format
> as.Date("2018-12-13 11:00:01 EST", format="%Y-%m-%d")
[1] "2018-12-13"
If all values are in a vector:
x = c("2018-12-13 11:00:01 EST", "2018-10-23 22:00:01 EDT",
"2018-11-03 14:15:00 EDT", "2018-10-04 19:30:00 EDT",
"2018-11-10 17:15:31 EST", "2018-10-05 13:30:00 EDT")
> as.Date(x, format="%Y-%m-%d")
[1] "2018-12-13" "2018-10-23" "2018-11-03" "2018-10-04" "2018-11-10"
[6] "2018-10-05"
I want to join a list of time zones into one long vector. Append seems to convert the time zones into the system time zone? Why?
> times = list(as.POSIXct("2015-01-01", tz = 'UTC', origin = "1970-01-01"),
+ as.POSIXct("2015-01-02", tz = 'UTC', origin = "1970-01-01"))
> times
[[1]]
[1] "2015-01-01 UTC"
[[2]]
[1] "2015-01-02 UTC"
> do.call(append, times)
[1] "2014-12-31 19:00:00 EST" "2015-01-01 19:00:00 EST"
I can't use unlist as it strips the list of the POSIXct class. What is the alternative?
I cannot get R to format POSIXlt objects in the desired timezone. POSIXct works as expected. Is this a bug or am I missing something?
date.str = "2015-12-09 13:30"
from = "Europe/London"
to = "America/Los_Angeles"
lt = as.POSIXlt(date.str, tz=from)
format(lt, tz=to, usetz=TRUE)
#[1] "2015-12-09 13:30:00 GMT"
ct = as.POSIXct(date.str, tz=from)
format(ct, tz=to, usetz=TRUE)
#[1] "2015-12-09 05:30:00 PST"
The tzone attributes are the same:
attributes(ct)$tzone
#[1] "Europe/London"
attributes(lt)$tzone
#[1] "Europe/London"
Solution
As pointed out by #nicola, format.POSIXlt has no tz parameter. To print a POSIXlt date in another timezone one can use lubridate package to convert a POSIXlt object to the desired timezone first:
require(lubridate)
lt.changed = with_tz(lt, tz=to)
format(lt.changed, usetz=TRUE)
#[1] "2015-12-09 05:30:00 PST"
I need to use as.Date on the index of a zoo object. Some of the dates are in BST and so when converting I lose a day on (only) these entries. I don't care about one hour's difference or even the time part of the date at all, I just want to make sure that the dates displayed stay the same. I'm guessing this is not very hard but I can't manage it. Can somebody help please?
class(xtsRet)
#[1] "xts" "zoo"
index(xtsRet)
#[1] "2007-07-31 BST" "2007-08-31 BST" "2007-09-30 BST" "2007-10-31 GMT"
class(index(xtsRet))
#[1] "POSIXt" "POSIXct"
index(xtsRet) <- as.Date(index(xtsRet))
index(xtsRet)
#[1] "2007-07-30" "2007-08-30" "2007-09-29" "2007-10-31"
Minimally reproducible example (not requiring zoo package):
my_date <- as.POSIXct("2007-04-01") # Users in non-UK timezone will need to
# do as.POSIXct("2007-04-01", "Europe/London")
my_date
#[1] "2017-04-01 BST"
as.Date(my_date)
#[1] "2017-03-31"
Suppose we have this sample data:
library(zoo)
x <- as.POSIXct("2000-01-01", tz = "GMT")
Then see if any of these are what you want:
# use current time zone
as.Date(as.character(x, tz = ""))
# use GMT
as.Date(as.character(x, tz = "GMT"))
# set entire session to GMT
Sys.setenv(TZ = "GMT")
as.Date(x)
Also try "BST" in place of "GMT" and note the article on dates and times in R News 4/1 .
You can offset the POSIX objects so its not based around midnight. 1 hour (3600 secs) should be sufficient:
d <- as.POSIXct(c("2007-07-31","2007-08-31","2007-09-30","2007-10-31"))
d
[1] "2007-07-31 BST" "2007-08-31 BST" "2007-09-30 BST" "2007-10-31 GMT"
as.Date(d)
[1] "2007-07-30" "2007-08-30" "2007-09-29" "2007-10-31"
as.Date(d+3600)
[1] "2007-07-31" "2007-08-31" "2007-09-30" "2007-10-31"
I would suggest using as.POSIXlt to convert to a date object, wrapped in as.Date:
d <- as.POSIXct(c("2007-07-31","2007-08-31","2007-09-30","2007-10-31"))
d
[1] "2007-07-31 BST" "2007-08-31 BST" "2007-09-30 BST" "2007-10-31 GMT"
as.Date(as.POSIXlt(d))
[1] "2007-07-31" "2007-08-31" "2007-09-30" "2007-10-31"
Achieves the same thing as the +3600 above, but slightly less of a hack
I'm trying to convert a yearmon date (from the zoo package) to a POSIXct in the UTC timezone.
This is what I tried to do:
> as.POSIXct(as.yearmon("2010-01-01"), tz="UTC")
[1] "2010-01-01 01:00:00 CET"
I get the same when I convert a Date:
> as.POSIXct(as.Date("2010-01-01"),tz="UTC")
[1] "2010-01-01 01:00:00 CET"
The only way to get it to work is to pass a character as an argument:
> as.POSIXct("2010-01-01", tz="UTC")
[1] "2010-01-01 UTC"
I looked into the documentation of DateTimeClasses, tzset and timezones. My /etc/localtime is set to Europe/Amsterdam. I couldn't find a way to set the tz to UTC, other than setting the TZ environment variable:
> Sys.setenv(TZ="UTC")
> as.POSIXct(as.Date("2010-01-01"),tz="UTC")
[1] "2010-01-01 UTC"
Is it possible to directly set the timezone when creating a POSIXct from a yearmon or Date?
Edit:
I checked the functions as.POSIXct.yearmon. This one passes to the as.POSIXct.Date.
> zoo:::as.POSIXct.yearmon
function (x, tz = "", ...)
as.POSIXct(as.Date(x), tz = tz, ...)
<environment: namespace:zoo>
So like Joshua says the timezone gets lost in the as.POSIXct.Date. For now I'll use Richies suggestion to set the tzone by hand using:
attr(x, "tzone") <- 'UTC'
This solves the issue of the lost tzone, which is only used for presentation and not internally like Grothendieck and Dwin suggested.
This is because as.POSIXct.Date doesn't pass ... to .POSIXct.
> as.POSIXct.Date
function (x, ...)
.POSIXct(unclass(x) * 86400)
<environment: namespace:base>
You are setting the timezone correctly in your code. The problem you are perceiving is only at the output stage. POSIX values are all referenced to UTC/GMT. Dates are assumed to be midnight times. Midnight UTC is 1 AM CET ( which is apparently where you are).
> as.POSIXct(as.yearmon("2010-01-01"), tz="UTC")
[1] "2009-12-31 19:00:00 EST" # R reports the time in my locale's timezone
> dtval <- as.POSIXct(as.yearmon("2010-01-01"), tz="UTC")
> format(dtval, tz="UTC") # report the date in UTC note it is the correct date ... there
[1] "2010-01-01"
> format(dtval, tz="UTC", format="%Y-%m-%d ")
[1] "2010-01-01 " # use a format string
> format(dtval, tz="UTC", format="%Y-%m-%d %OS3")
[1] "2010-01-01 00.000" # use decimal time
See ?strptime for many, many other format possibilities.
In the help page ?as.POSIXct, for the tz argument it says
A timezone specification to be used
for the conversion, if one is
required. System-specific (see time
zones), but ‘""’ is the current
timezone, and ‘"GMT"’ is UTC
(Universal Time, Coordinated).
Does as.POSIXct(as.yearmon("2010-01-01"), tz="GMT") work for you?
After more perusal of the documentation, in the details section we see:
Dates without times are treated as
being at midnight UTC.
So in your example, the tz argument is ignored. If you use as.POSIXlt it is easier to see what happens with the timezone. The following should all give the same answer, with UTC as the timezone.
unclass(as.POSIXlt(as.yearmon("2010-01-01")))
unclass(as.POSIXlt(as.yearmon("2010-01-01"), tz = "UTC"))
unclass(as.POSIXlt(as.yearmon("2010-01-01"), tz = "GMT"))
unclass(as.POSIXlt(as.yearmon("2010-01-01"), tz = "CET"))
In fact, since you are using as.yearmon (which strips the time out) you will never get to set the timezone. Compare, e.g.,
unclass(as.POSIXlt(as.yearmon("2010-01-01 12:00:00"), tz = "CET"))
unclass(as.POSIXlt("2010-01-01 12:00:00", tz = "CET"))
This seems to be an oddity with the date/time "POSIXct" class methods. Try formatting the "Date" or "yearmon" variable first so that as.POSIXct.character rather than as.POSIXct.{Date, yearmon} is dispatched:
Date
> d <- as.Date("2010-01-01")
> as.POSIXct(format(d), tz = "UTC")
[1] "2010-01-01 UTC"
yearmon
> library(zoo)
> y <- as.yearmon("2010-01")
> as.POSIXct(format(y, format = "%Y-%m-01"), tz = "UTC")
[1] "2010-01-01 UTC"
> # or
> as.POSIXct(format(as.Date(y)), tz = "UTC")
[1] "2010-01-01 UTC"