I have a vector a = 40208.64507.
In excel, I can automatically change a to a datetime: 2010/1/30 15:28:54 by click the Date type.
I tried some methods but I cannot get the same result in R, just as in excel.
a = 40208.64507
# in Excel, a can change into: 2010/1/30 15:28:54
as.Date(a, origin = "1899-12-30")
lubridate::as_datetime(a, origin = "1899-12-30")
Is there any way to get the same results in R as in Excel?
Here are several ways. chron class is the closest to Excel in terms of internal representations -- they are the same except for origin -- and the simplest so we list that one first. We also show how to use chron as an intermediate step to get POSIXct.
Base R provides an approach which avoids package dependencies and lubridate might be used if you are already using it.
1) Add the appropriate origin using chron to get a chron datetime or convert that to POSIXct. Like Excel, chron works in days and fractions of a day, but chron uses the UNIX Epoch as origin whereas Excel uses the one shown below.
library(chron)
a <- 40208.64507
# chron date/time
ch <- as.chron("1899-12-30") + a; ch
## [1] (01/30/10 15:28:54)
# POSIXct date/time in local time zone
ct <- as.POSIXct(ch); ct
## [1] "2010-01-30 10:28:54 EST"
# POSIXct date/time in UTC
as.POSIXct(format(ct), tz = "UTC")
## [1] "2010-01-30 10:28:54 UTC"
2) Using only base R convert the number to Date class using the indicated origin and then to POSIXct.
# POSIXct with local time zone
ct <- as.POSIXct(as.Date(a, origin = "1899-12-30")); ct
## [1] "2010-01-30 10:28:54 EST"
# POSIXct with UTC time zone
as.POSIXct(format(ct), tz = "UTC")
## [1] "2010-01-30 15:28:54 UTC"
3) Using lubridate it is similar to base R so we can write
library(lubridate)
# local time zone
as_datetime(as_date(a, origin = "1899-12-30"), tz = "")
[1] "2010-01-30 15:28:54 EST"
# UTC time zone
as_datetime(as_date(a, origin = "1899-12-30"))
[1] "2010-01-30 15:28:54 UTC"
Related
Trying to get current date in a POSIXct class. I have tried the following:
as.POSIXct(Sys.Date(), format = "%m/%d/%y", tz = "EST")
and got
[1] "2021-02-12 19:00:00 EST"
and I wish to only get the date without the time but in POSIXct class. For instance:
[1] "2021-02-12"
Convert the Date class object to character first:
as.POSIXct(format(Sys.Date()))
## [1] "2021-02-13 EST"
Even shorter is:
trunc(Sys.time(), "day")
## [1] "2021-02-13 EST"
Note:
POSIXct objects are stored internally as seconds since the Epoch and not as separate date and time so they always have times; however, if the time is midnight as it is here then it does not display when printed using the default formatting.
if you only need the Date it is normally better to use Date class since using POSIXct class can result in subtle time zone errors if you are not careful and there is typically no reason to expose yourself to that potential if you don't need to.
if you change the session's time zone then it won't display without the time because midnight in one time zone is not midnight other time zones.
x <- as.POSIXct(format(Sys.Date()))
x
## [1] "2021-02-13 EST"
# change time zone
Sys.setenv(tz = "GMT")
x
## [1] "2021-02-13 05:00:00 GMT"
# change back
Sys.setenv(tz = "")
x
## [1] "2021-02-13 EST"
I have almost finished my script but I have a problem with my dates format.
I installed lubridate package used the as_date function, but it doesn't give me what I want (a date).
"time" is my variable, I put its description below.
I do not put my entire script since the concern is only about this format question (and it implies a huge netcdf file impossible to download)
Could you help me please ?
class(time)
[1] "array"
head(time)
[1] 3573763200 3573774000 3573784800 3573795600 3573806400 3573817200
tunits
$long_name
[1] "time in seconds (UT)"
$standard_name
[1] "time"
$units
[1] "seconds since 1900-01-01T00:00:00Z"
$axis
[1] "T"
$time_origin
[1] "01-JAN-1900 00:00:00"
$conventions
[1] "relative number of seconds with no decimal part"
#conversion
date = as_date(time,tz="UTC",origin = "1900-01-01")
head(date)
[1] "-5877641-06-23" "-5877641-06-23" "-5877641-06-23" "-5877641-06-23"
[5] "-5877641-06-23" "-5877641-06-23"
Time is in seconds since 01/01/1900. Converting a value in time to an actual date would work as follows, using the seconds methods in lubridate:
lubridate::ymd("1900-01-01") + lubridate::seconds(3573763200)
You can vectorize it:
lubridate::ymd("1900-01-01") + lubridate::seconds(time)
as_date() calculates the date using the number of days since the origin.
What you are looking for seems to be as_datetime() also from the lubridate package which calculates the date using the number of seconds since the origin. In your example this would be:
time <- c(3573763200,3573774000,3573784800,3573795600,3573806400,3573817200)
date <- as_datetime(time, tz = "UTC", origin = "1900-01-01") %>% date()
Using a dplyr pipe and the date() function from lubridate to extract the date from the as_datetime() function.
date <- as_date(time/(24*60*60), tz = "UTC", origin = "1900-01-01")
date
When I try to coerce a POSIXct date-time to a Date using as.Date, it seems to return wrong date.
I suspect it has got something to do with the time zone. I tried the tz argument in as.Date, but it didn't give the expected date.
# POSIXct returns day of month 24
data$Time[3]
# [1] "2020-03-24 00:02:00 IST"
class(data$Time[3])
# [1] "POSIXct" "POSIXt"
# coerce to Date, returns 23
as.Date(data$Time[3])
# [1] "2020-03-23"
# try the time zone argument, without luck
as.Date(data$Time[3], tz = "IST")
# [1] "2020-03-23"
# Warning message:
# In as.POSIXlt.POSIXct(x, tz = tz) : unknown timezone 'IST'
Sys.timezone()
# [1] "Asia/Calcutta"
Any ideas what may be going wrong here?
Using the setup in the Note at the end we can use any of these:
# same date as print(x) shows
as.Date(as.character(x))
## [1] "2020-03-24"
# use the time zone stored in x (or system time zone if that is "")
as.Date(x, tz = attr(x, "tzone"))
## [1] "2020-03-24"
# use system time zone
as.Date(x, tz = "")
## [1] "2020-03-24"
# use system time zone
as.Date(x, tz = Sys.timezone())
## [1] "2020-03-24"
# use indicated time zone
as.Date(x, tz = "Asia/Calcutta")
## [1] "2020-03-24"
Note
We have assumed this setup.
Sys.setenv(TZ = "Asia/Calcutta")
x <- structure(1584988320, class = c("POSIXct", "POSIXt"), tzone = "")
R.version.string
## [1] "R version 4.0.2 Patched (2020-06-24 r78745)"
The clue is in the warning message. as.Date() doesn't know how to interpret IST as a timezone and so defaults to UTC. Assuming that IST is Indian Standard Time (rather than Irish Standard time) and that IST is UTC+5:30, as.Date() is giving the expected result, even if it is incorrect for your purposes.
Providing a date with a timezone expressed as an offset from UTC gives the desired result.
as.Date("2020-03-24 00:02:00 UTC+5:30")
[1] "2020-03-24"
I have a Time column in my df with value 1.01.2016 0:00:05. I want it without the seconds and therefore used df$Time <- as.POSIXct(df$Time, format = "%d.%m.%Y :%H:%M", tz = "Asia/Kolkata"). But I get NA value. What is the problem here?
I suspect there are two things working here: the storage of a time object (POSIXt), and the representation of that object.
The string you present is (I believe) not a proper POSIXt (whether POSIXct or POSIXlt) object for R, which means it is just a character string. In that case, you can remove it with:
gsub(':[^:]*$', '', '1.01.2016 0:00:05')
# [1] "1.01.2016 0:00"
However, that is still just a string, not a date or time object. If you parse it into a time-object that R knows about:
as.POSIXct("1.01.2016 0:00:05", format = "%d.%m.%Y %H:%M:%S", tz = "Asia/Kolkata")
# [1] "2016-01-01 00:00:05 IST"
then you now have a time object that R knows something about ... and it defaults to representing it (printing it on the console) with seconds-precision. Typically, all that is available to change for the console-printing is the precision of the seconds, as in
options("digits.secs")
# $digits.secs
# NULL
Sys.time()
# [1] "2018-06-26 18:21:06 PDT"
options("digits.secs"=3)
Sys.time()
# [1] "2018-06-26 18:21:10.090 PDT"
then you can get more. But alas, I do know think there is an R-option to say "always print my POSIXt objects in this way". So your only choice is (at the point where you no longer need it to be a time-like object) to change it back into a string with no time-like value:
x <- as.POSIXct("1.01.2016 0:00:05", format = "%d.%m.%Y %H:%M:%S", tz = "Asia/Kolkata")
x
# [1] "2016-01-01 00:00:05 IST"
?strptime
# see that day-of-month can either be "%d" for 01-31 or "%e" for 1-31
format(x, format="%e.%m.%Y %H:%M")
# [1] " 1.01.2016 00:00"
(This works equally well for a vector.)
Part of me suggests convert to POSIXt and back to string as opposed to my gsub example because using as.POSIXct will tell you when the string does not match the date-time-like object you are expecting, whereas gsub will happily do something wrong or nothing.
Try asPOSIXlt:
> test <- "1.01.2016 0:00:05"
> as.POSIXlt(test, "%d.%m.%Y %H:%M:%S", tz="Asia/Kolkata")
[1] "2016-01-01 00:00:05 IST"
The date in my dataset is like this: 20130501000000 and I'm trying to convert this to a better datetime format in R
data1$date <- as.Date(data1$date, format = "%Y-%m-%s-%h-%m-%s")
However, I get an error for needing an origin. After I put the very first cell under date in as origin, it converts every cell under date to N/A. Is this right or should I try as.POSIXct()?
That is a somewhat degenerate format, but the anytime() and anydate() functions of the anytime package can help you, without requiring any explicit format strings:
R> anytime("20130501000000") ## returns POSIXct
[1] "2013-05-01 CDT"
R> anydate("20130501000000") ## returns Date
[1] "2013-05-01"
R>
Not that we parse from character representation here -- parsing from numeric would be wrong as we use a conflicting heuristic to make sense of dates stored a numeric values.
So here your code would just become
data1$data <- anytime::anydate(data1$date)
provided data1$date is in character, else wrap one as.character() around it.
Lastly, if you actually want Datetime rather than Date (as per your title), don't use anydate() but anytime().
Before I write my answer, I would like to say that the format argument should be the format that your string is in. Therefore, if you have "20130501000000", you have to use (you don't have - between each component of your date in the string format):
as.Date("20130501000000", format = "%Y%m%d%H%M%S")
# [1] "2013-05-01"
which works just fine, does not produce any error, and will return an object of class Date:
as.Date("20130501000000", format = "%Y%m%d%H%M%S") |> class()
# [1] "Date"
Therefore, I think your issue is more of a formatting and not origin of the date.
Now to my detailed answer:
As far as I know and can understand, the as.Date() will convert it to "date", so if you want the time part of the string as well, you have to use as.POSIXct():
as.POSIXct("20130501000000", format = "%Y%m%d%H%M%S")
# [1] "2013-05-01 EEST"
as.POSIXct("20130501000000", format = "%Y%m%d%H%M%S") |> class()
# [1] "POSIXct" "POSIXt"
Note that the timezone is EEST which is my local timezone, if you want to define the timezone, you have to define it. For example to set the timezone to UTC:
as.POSIXct("20130501000000", format = "%Y%m%d%H%M%S", tz = "UTC")
# [1] "2013-05-01 UTC"
using the as.POSIXct() you can do arithmetic with the object:
times <- c("20130501000000",
"20130501035001") # added 03:50:01 to the first element
class(times)
# [1] "character"
times <- as.POSIXct(times, format = "%Y%m%d%H%M%S", tz = "UTC")
class(times)
# [1] "POSIXct" "POSIXt"
times[2] - times[1]
# Time difference of 3.833611 hours